anything from Rise of the Robots
The ED-209 thing from Captive for being so blatent.
The Dalek thing from Captive 2 for looking crap.
Walker for looking as cool as ED-209 itself.
Robocod for being a fish.
The Probe droid in Empire Strikes back for using ring-modulation.
The Mechanoids from Wipe Out for being in Wipe Out.