I've seen hackers in virtual person in TF2 on a Valve server. Permanent crits and a text spamming script. I've also seen infinite jumps and invulnerability in Metroid Prime Hunters, and modded weapons which crashed the game in the first Borderlands. Resident Evil 5 also has some glitches and hacks for infinite healing items and ridiculous weapons. Wut bout you, Flood? What games and what hacks have you seen?