Functions and slash commands found in SuperMacro addon that can be helpful in your macros are listed here in alphabetical order. Alt-click on an item to insert its item link into the macro.

(For even more convenience and to shorten macros, I recommend another addon, Alias, a.k.a ASF. Read end of file for explanation.)

(P.S. I may accept requests for other convenient functions and slash commands.)

--Table of Contents
CancelBuff(buff [,...]), unbuff
cast
caststop(spell [,...])
Channel(spell), /smchan, /smchannel
CraftItem( skill, item, count), /craft, /smcraft
DoOrder(spell | item [,...]), /order, /smorder
echo
/equip, /smequip, /eq, /smeq
/equipoff, /smequipoff, /eqoff, /smeqoff
Fail(message), /fail
FindBuff(buff [ [, unit], item]), buffed
FindItem(item)
/in seconds[+] command, SM_IN(seconds, command, repeat)
Macro
Pass(message), /pass
pickup(bag, slot), pickup(inventory_slot), pickup("item")
/print msg, /smprint, SM_print(msg), echo
PrintColor(r,g,b,msg [,...]), Printc
Printd(msg [,...]), Print
PrintTable(table, rowname, level), Printt
RunBody(longtext)
RunLine(command [,...])
RunMacro(index|macro), Macro, /macro
RunSuperMacro(index|super)
SayRandom(speech [,...]), /sayrandom, /smsayrandom
send
SetActionMacro(actionid, macro)
SetActionSuperMacro(actionid, supername)
/shift form -- for druids, rogues, warriors only
stopcast
/unequip, /smunequip, /uneq, /smuneq
use(bag,slot), use(item), /use, /smuse
UseItemByName(item)
## Alias
--End table of contents

## CancelBuff(buff [,...]), unbuff, /unbuff, /smunbuff
Cancel the player's buffs that match the given strings.
Ex. /script CancelBuff("Demon Skin")
Ex. /script CancelBuff("demon") -- cancel buffs with demon in it, including Demon Skin
Ex. /script unbuff("demon") -- same as above
Ex. /unbuff demon -- same as above
Ex. /unbuff mana, frost -- cancel any buffs matching mana or frost
Ex. /unbuff . -- cancel all buffs, use with care
Ex. /unbuff a -- careful, cancel all buffs with 'a' in their names

## cast
cast is same as CastSpellByName.
Ex. cast("Heal")

## caststop(spell [,...])
Cast a spell, then stop. Will cast multiple spells in sequence. Only works properly for spells that don't cause global cooldown. (Not tested.)
Ex. /script caststop("Arcane Power","Presence of Mind","Frostbolt")
is equivalent to
/cast Arcane Power
/script SpellStopCasting();
/cast Presence of Mind
/script SpellStopCasting();
/cast Frostbolt

## Channel(spell), /smchan, /smchannel
Safely channel a spell, ignoring accidental multiple keypresses.
Ex. SM_Channel("mind flay")
Ex. /smchan mind flay
-- test tooltip

## CraftItem( skill, item, count), /craft, /smcraft
Create item or enchant (at least one time). If count is left out (nil) then will make one. If count is zero, then will make all available. If count is negative, then will leave that much.
Ex. /craft First aid, Heavy Linen Bandage -- make one bandage
Ex. /smcraft First aid, Heavy Linen Bandage, 0 -- make all available bandages
Ex. CraftItem( "First aid", "Heavy Linen Bandage", -1 ) -- make all but one

## DoOrder(...), /order, /smorder
Use first available item or cast spell in a list separated by commas, and ignore the rest of the list. Alt-click on item to insert item link into macro.
Ex. DoOrder("healing potion", "lesser healing potion", "healing touch")
Ex. /order healing potion, lesser healing potion, healing touch
-- if healing potion found, will use it, and ignore the rest of the list

## echo
See /print.

## /equip, /smequip, /eq, /smeq
Equip or use an item. Also works with item links. Alt-click on item to insert item link into macro.
Ex. /eq hatchet

## /equipoff, /smequipoff, /eqoff, /smeqoff
Equip item into off-hand slot. Also works with item links. Alt-click on item to insert item link into macro.
Ex. /eqoff shield

## Fail(message), /fail
Run message or script if current action (spell or item) failed. See Pass for success.
Ex. /script CastSpellByName("Attack") Fail("Can't attack")
Ex. /script CastSpellByName("nada") Fail("not a spell")
Ex. /script Fail("no action")
Ex. /fail /script use('hearthstone')
Ex.
/cast Heal
/fail /p can't heal

## FindBuff, buffed
See if a unit has a specific buff or debuff, or weapon buff.
Usage 1: FindBuff(buff [ [, unit], item])
Usage 2: buffed(buff [ [, unit], item])
buff is the buff's name, or part of it's name--not case sensitive
unit is API 'unit' value ('player' if left empty or nil)
item value is boolean. if item is not nil or false or empty, then will search for item buff instead
Ex. buffed("Find Herbs") -- player's buff; returns "track", 0
Ex. buffed("herbs") -- also works
Ex. FindBuff("rockbiter",nil,1) -- player's weapon buff; returns "main" or "off", time left, charges
Ex. buffed("rockb") -- same as above
Ex. buffed("gouge", 'target') -- target's buff; returns "debuff", id
Ex. buffed("perception") -- returns "buff", id

## FindItem(item)
Find an item in your container bags or inventory. If found in inventory, returns slot, nil, texture, count. If found in bags, returns bag, slot, texture, total count in all bags. Also works with item links. Alt-click on item to insert item link into macro.
Ex. local bag,slot,texture,count = FindItem("Lesser Magic Essence");

## /in seconds[+] command, /smin, SM_IN(seconds, command[, repeat])
Execute command in seconds seconds. Use + after sec to repeat. Separate multiple commands with \n. Does not cast spells or use items. 
Ex. /in 5 /p NOW
Ex. /script SM_IN(5, "/p NOW") -- same as first, no repeat
Ex. /in 1 /script PlaySound( "LOOTWINDOWCOINSOUND")
Ex. /smin 600+ /print 10 mins repeating -- use + to repeat
Ex. SM_IN(600, "/print 10 mins repeating", 1) -- repeats, same as above, but no +, instead include third parameter
Ex. /in 1 /t ;me hi\n/t ;me hey -- multiple commands separated by \n
Ex. /script SM_IN(1,"/t ;me hi\n/t ;me hey") -- same as above
Ex. /in 1m /print 1 min passed -- 1m = 1 minute, 1h = 1 hour, 1s = 1 second
Ex. /script SM_IN("1m","/print 1 min passed") -- same as above, note 1m in quotes
Ex. /in 1h30m5s+ /print repeat every hour and 30 mins and 5 seconds

## Macro
See RunMacro.

## Pass(message), /pass
Run message or script if current action (spell or item) succeeded. See Fail for failure.
Ex. /script CastSpellByName("Attack") Pass("Attacking")
Ex. /pass /macro Cheer
Ex.
/cast Heal
/pass /p Healing

## pickup(bag, slot), pickup(inventory_slot), pickup("item")
Pickup item from inventory or bags. One argument for inventory; two arguments for bags. Argument can also be a string containing the item's name. Calling this function again puts the item into that slot, which may swap items. Also works with item links. Alt-click on item to insert item link into macro.
Ex. pickup(16) --main hand weapon
Ex. pickup("mainhandslot") -- also main hand weapon
Ex. pickup(1,4) -- bag 1, 4th slot
Ex. pickup("hearthstone") -- pickup hearthstone
Ex. pickup("hearthstone") pickup("healing potion") -- consecutive pickups will swap these items
Ex. pickup("hearthstone") pickup(4,7) -- put hearthstone in that slot; may swap if slot is not empty
Ex. pickup("ring of iron will") pickup("finger0slot") -- put ring on first finger slot

## /print msg, /smprint, SM_print(msg), echo
Print message into chat that only you can see. It's identical to DEFAULT_CHAT_MESSAGE:AddMessage. Default color is white, but you can change it in options.
Ex. /print test
Ex. echo("test")

## PrintColor(r,g,b,...), Printc
Print message into chat that only you can see using specified color codes, in order of red, green, and blue. Color values are between 0 and 1. Also accepts any number of arguments like Printd.
Ex. PrintColor(1,0,1, "test") -- purple
Ex. PrintColor(1,1,0, "msg1", "msg2") -- yellow

## Printd(...), Print
Print message into chat that only you can see. Unlike /print, this accepts any number of arguments and prints each onto separate lines. Also, color is always white. If Print is taken by another addon, it will not overwrite it.
Ex. Printd("Test")
Ex. Print("msg 1", "msg 2") -- only if another addon doesn't have Print

## PrintTable(table, row, level), Printt
Print a table into chat for your view only.
Ex. PrintTable(SM_VARS)

## RunBody(longtext)
Execute longtext like a macro. Each line is separated by \n.
Ex. RunBody("/cast Attack\n/pass /p Attack!")
Ex. /in 5 /script RunBody("/print 5 secs passed\n/macro MyMacro")

## RunLine(...)
Execute a line like a macro or chat message. Takes multiple lines, where each line is another argument separated by commas. Excellent for doing slash commands within 'if' blocks.
Ex. RunLine("/p hi")
Ex. RunLine("/p hi", "/dance", "/supermacro")
Ex. if GetSpellCooldown(1,'spell')==0 then CastSpell(1,'spell') RunLine("/in 5 /print Cooldown finished") end

## RunMacro(index | name), Macro, /macro
Execute a macro by name or by index.
Ex. /macro Attack -- runs macro named Attack
Ex. RunMacro("Attack") -- same as above
Ex. Macro(1) -- run first macro in macro frame
Ex. /macro 1 -- will run macro named 1; note difference from last example
Ex. Macro("1") -- same as last example
Ex. /macro -- opens SuperMacro frame (no argument passed)

## RunSuperMacro(index | super)
Execute a SuperMacro by name or by index (in the order shown in SuperMacro frame at Super tab).
Ex. RunSuperMacro(1);
Ex. RunSuperMacro("MySuperMacro");

## SayRandom(...), /sayrandom, /smsayrandom
Say a random phrase from a list separated by comma. Actually, you can do more than send chat messages. There's an equal chance (1 in number of list items+1) that nothing will happen.
Ex. /sayrandom hi, hello -- says hi or hello or nothing
Ex. /script SayRandom("hi","hello"); -- same as last example
Ex. /script SayRandom("/script Print(1)","/script Print(2)"); -- actions besides chat
Ex. /sayrandom /script Print(1), /script Print(2) -- same as last example

## send
send is same as SendChatMessage. Also see RunLine.
Ex. send("hi") -- send "hi" to local channel
Ex. send("hi", "WHISPER", "COMMON", "Aquendyn") -- send whisper

## SetActionMacro(actionid, macro)
Set or replace an action button with another macro. The global variable lastActionUsed can be used to get the ID of the last action button that was pressed or clicked.
Ex. Swap two macros named FindHerbs and FindMinerals.

Macro FindHerbs looks like this:
/cast Find Herbs

/script SetActionMacro( lastActionUsed, 'FindMinerals' )

Macro FindMinerals looks like this:
/cast Find Minerals

/script SetActionMacro( lastActionUsed, 'FindHerbs' )

Drag either macro into an action button on your action bar. Each time you execute that action, the macros will swap, along with their appropriate icons and tooltips.

## SetActionSuperMacro(actionid, supername)
Set or replace an action button with a SuperMacro. The global variable lastActionUsed can be used to get the ID of the last action button that was pressed or clicked. See SetActionMacro for an example.
Ex. SetActionSuperMacro(1,"MySuperMacro");

## /shift form
Form is number or name of form, stealth, or stance.
Druids: bear=1, aquatic=2, cat=3, travel=4, moonkin=5
Rogues: stealth=1
Warriors: battle=1, defend=2, berzerk=3
Ex. /shift bear
Ex. /shift battle
Ex. /shift stealth
Ex. /shift 1 -- all four commands are equivalent, any of them will shift to battle for warriors, stealth for rogues, bear for druids

## stopcast
stopcast is same as SpellStopCasting
Ex.
/cast Arcane Power
/script stopcast()

## /unequip, /smunequip, /uneq, /smuneq
Unequip an item if you have an empty bag space. Alt-click on item to insert item link into macro.
Ex. /uneq shield

## use, /use, /smuse
Use an item by name or link, by bag and slot, or by inventory slot. Alt-click on item to insert item link into macro.
Ex. /use hearthstone
Ex. /use 4,1
Ex. /script use("hearthstone");
Ex. /script use(4,1); -- bag 4, 1st slot
Ex. /script use(13); -- trinket

## UseItemByName(item)
Use or equip an item given its name or item link. Alt-click on item to insert item link into macro.
Ex. UseItemByName("hearthstone")

#############
#
## Aliases to simplify macros
#
############
Aliases can simplify your macros significantly.
For example, to get current mana, alias is simply ;pm--instead of UnitMana('player'). More importantly, Alias allows values from functions into chat. Instead of:
/script SendChatMessage("Buffing you", "WHISPER", "COMMON", UnitName("target"))
use a regular chat message:
;tt Buffing you

Useful default aliases include:
;z for /script
;cn for CastSpellByName
;c for /cast
;m for /macro
;rl for /console reloadui
;pm for player mana
;pmm for player max mana
;ph for player health
;phm for player max health
;p2h for party2 health (and so on for party3, party4, party5)