These are the things that will be complete gamebreakers for me, as in if I even catch wind of it I'm avoiding (I take a big risk buying FPS games because I don't like 90% of them)
-Bunnyhopping
-"K-Walking" (exploiting some glitch or spam a button to move faster)
-"Sniper" mass (I already know there are no one shot kill snipers, but it still can happen)
-Freak Dancing (Spamming left and right keys to dodge bullets, it's like you're on ice or something)
-Mass camping (particularly spawn camping)
-Funneling (Choke points with no way around for anyone)
-Pea shooters (I'm not talking one shot kill, but WAY less than BF2 or TF2)
-Source movement (basically, if it feels like a CSS when walking)
-Penalty for leaving a match
-Noob-tubing (Grenade spam, sticky camping, mass explosives basically)
-Bunnyhopping (This is the big one, the ultimate turn off, I will never play a game that has bunnyhopping in it)
-Fairy jumps (Tap space bar for instant leap, looks like you're floating instead of having to coil your muscles to jump)
I'm not sure if I can edit after a long term, but any civilized answers would be nice. I've never found an FPS game I liked but Brink really looks like I could enjoy the light build Spy type gameplay.