Its only cheap if it's game-breaking, that is if the tactic will guarantee victory or guarantee the kill in any case, or forces other players to adapt to it if they want to win. To go outside the realm of FPS, snaking was game-breaking in Mario Kart DS, where it came down to a matter of snake or lose
To look back inside the realm of FPS, the noob combo from Halo 2 (i believe Plasma Gun x Needler? Didn't play it much as i never had an Xbox), but while it guaranteed a kill if it connected, players skilled enough could get around it
Camping *can* be game-breaking, but that depends on the mechanics game-by-game, and even then depends on match types (like if its a team battle, camping is okay because you have to get all the way to the other side of the map to do it, which is hard enough in itself, and nowhere is safe in a free-for-all usually, but that all depends)
Monster Hunter: pissing me off since 2010.
