I'm looking for a word which describes an annoying behavior that decreases the overall quality of a game or match, specifically in online gaming (Halo, Call of Duty, etc.) The behavior, while not expressly prohibited by the rules and thus not technically cheating, is generally agreed to be undesirable or even unfair by the other players and puts the offending player at a distinct advantage.
The following words come to mind, but do not precisely fit: annoying (too broad), trolling (mismatched intent; the player is still trying to win the game, not merely annoy others), ungentlemanly (I'd prefer an genderless term.)
I believe unsportsmanlike could be a good fit; I'm looking for either a better fitting word, or a sound justification that one of these words is correct.
edit: To be clear, I am looking for an adjective to levy at someone as an insult for behaving in this way. Also, the interest of the offending player is to win the game at the expense of others. The example camping in the comments is precisely the kind behavior I'm talking about.
I'd like to complete this sentence:
Don't camp; that's ______.