The best is the Scavenger, which has nothing to do with scavenging. It’s a sphere with three thin tentacles, and it scampers along at ground level rather than standing upright on them. It’s horrific enough just watching it move, but it can also send out a hovering attack drone, or tuck its legs into its chassis and roll around like a boulder. Controlling it then is like playing Marble Madness on UT3’s maps, swerving up hills to pick up momentum to squish more people.
The other best is the Viper, a large, sleek hoverbike that fires a torrent of bouncing energy shuriken. It’s a grisly thrill to swing its heavy yet frictionless form sideways into a trio of enemies for a triple vehicular manslaughter multikill, and it’s one of the few things fast enough to reliably avoid the gaze of a Dark Walker’s killer laser-eyes. But the Viper’s ultimate trick, in both senses of the word, only occurs when it jumps. Its fins tilt backwards, and for the briefest moment an urgent beep indicates that the self-destruct function is primed. Hit the proper button, with your bike pointed at something important, and you eject powerfully into the air while your ride-turned-missile smashes into its target. Aiming that payload at the torso of a mighty Dark Walker and blowing it in twain is pure glory.