CCing Pets

This is one thing I'm sorta surprised I don't see that often. Alot of teams tend to either kill pets or just ignore them (or fake cast around spell lock, perhaps). CCing pets is a pretty powerful tool that will let you force cooldowns where you otherwise wouldn't have been able, albeit it's somewhat situational.

Example: You're on a warlock. His felhunter is on you. Frost nova it, then move around a corner before casting. I don't think I've ever seen a warlock command a felhunter to self-devour nova to deal with this (admittedly, devour is probably usually on cooldown from trying to catch sheeps), so you've just guaranteed yourself an easy 3-5 frostbolts without having to fake cast around spell lock. This is easier than ever with square pillars.

I also sometimes blow deep freezes on felhunters (usually just on openers, it makes it alot easier to force trinkets vs some comps). A guaranteed shatter with your entire team winding up on someone can be pretty brutal as pretty much any mage comp. Also, remember to try doing a quick fake as the felhunter comes out of deep freeze, there's a pretty good chance the warlock will be spamming spell lock going "wtf".

Sapping felhunters is a great way to get sheep to stick to warlock at the start of a match - it's a little hard to pull off on certain maps, and in 3v3 in general I find, but it's very powerful playing rogue mage in 2s (vs shaman lock especially, you can force all their cooldowns pretty much immediately with this strat if you do it right on most maps). Keep in mind that felhunters drop combat as soon as they stop moving to attack you, so while alot of warlocks will send their pets in to get in combat (and their pets as well), as soon as they pull it back to prevent you from beating it up, your rogue can sap and you can move in.

Sometimes you will be winding up a shatter vs a DK team and see the ghoul heading towards you (well, it will leap when it gets in range most likely). Usually if you're freecasting like this, the dk is going to use his ghoul to stun you, so try pet freezing it, ideally catching a player (probably your target) with it as well. The same principle applies to BM hunter pets somewhat - but frankly, most BM hunters aren't too concerned with using their pet stun to interrupt frostbolts I've found.