Warning: I will change these slash commands if I realize they are used by some other popular addon.

Adds the possibility to disable macro errors and sounds.

/de Disable all errors from macro.
/de 52 55 Disable errors 52 (Item is not ready yet) and 55 (Spell is not ready yet) from macro. The /de command accepts any number of error codes. Some other interesting ones are 331 (Not enough mana) and 364 (Out of range).
/dr Shortcut for /de 52 55
/ts Toggle sound

Example macro:

Macro explained:

First /ts disables sound so you don't here an annoying sound if you click again during GCD.
The /use 13 and /use 14 tries to use your trinkets.
The /cast [@mouseover] Rejuvenation casts Rejuvenation at your mouse over target.
Second /ts restores sound to whatever it was before the first call to /ts
The /dr is a shortcut for /de 52 55 and suppresses the "Item is not ready yet" and "Spell is not ready yet" errors. You will still get errors such as "Not enough mana" and "Out of range". If you want to disable all errors use /de without parameters.

Silentium