Plasma sword

Flashy joke

The plasma sword (or 'energy sword') is occasionally carried by gold Elites or cloaked Elites, but it holds very little threat as you should easily be able to take down the Elite before he gets close enough for a swing. It's bad news for Marines though; they'll get sliced up in no time if you don't help them. Worse, Marines don't seem to notice cloaked Elites carrying the sword, even though it's a dead give-away. You never get to use the sword yourself; it goes poof once the owner is killed.