Guilt has no place in Halo 2. So go ahead and rack up some cheap kills by finishing people off.

Scavenger

Make no mistake about it - if you want to finish near the top in Rumble Slayer on a regular basis, you must "steal kills from other players". There is no need to be a gentleman and wait for a battle to end before you swoop in and finish off a few weakened opponents. Well-tossed grenades can earn much needed double or triple kills from players battling each other afar off. This strategy is part of Halo and should be taken advantage of in any game variation.