Controlling button feedback and the question mark (?) icon with #show

By default, WoW uses the first spell or item that appears in a macro to show cooldown, range, and availability feedback on the button, and to pick which icon to display when you use the question mark icon. Take our multi-spell macro from earlier as an example:
/use Talisman of Ephemeral Power
/cast Arcane Power
/stopcasting
/cast Presence of Mind
/stopcasting
/cast Pyroblast

With this macro, WoW chooses Arcane Power for the feedback. However, this is probably not what you really want. The main point of this spell is to cast Pyroblast. The first few lines merely exist as support spells to make the Pyroblast more effective. You can make the button behave as if Pyroblast were the first spell by adding the following line to the top of the macro:
#show PyroblastIf you used the question mark icon for the macro, the button will even have the icon of Pyroblast without any extra effort on your part. The parameter to #show (in this case Pyroblast) works the same way as the /cast and /use commands. You can use a spell name, item name, item id (item:12345), inventory slot, or bag and slot numbers.

Similar to #show is #showtooltip. Normally when you mouse over a macro on an action bar, your tooltip displays the name of the macro. This is not incredibly useful most of the time (especially if you use an addon like TheoryCraft to give you detailed spell information in tooltips). However, the #showtooltip command allows you to specify a spell to use in the tooltip the same way as #show. If you use #showtooltip, you do not need to use #show.

If you're happy with the spell that WoW is choosing for the feedback, you can use #showtooltip without a spell to save space in your macro. WoW will still use whichever spell it was choosing before, but it will now show the tooltip info for that spell/item.

Please Note: unlike slash commands, #show and #showtooltip must be written in lower case letters.