Originally Posted by EvilMike

Ammo hacking: Look for things like people having a seemingly limitless supply of seekers, espically in levels or areas where they are not particularly abundant. People using powerups that aren't in the level is a dead giveaway, though most people aren't that stupid. Many are stupid enough, however, to spawn with full ammo. If you see someone firing a barrage of seekers the second after they spawn, you know something's up.