When I was younger... okay, no, scratch that - it was yesterday, I was driving home from work and got cut up a hell of a lot by other wretched motorists. What I really wanted was a massive Mech Warrior that I could crush their puny brains with underneath its gigantic feet. Now giant Mech Warriors are gosh darned difficult to come by, but the $300 BRAT kit is a whole lot easier.
Botmag have done a great big lovely review of the BRAT kit - a bipedal starter-set - that comes with everything from individually wrapped servos, anodised chassis and requisite screws and bearings, to a software option that lets you program each limb individually. BRAT can be added to with sensor arrays, arms, even circuit-boards that give it autonomy.
Sadly my robotics skills would probably require an even more basic "basic" set, but for all you enthusiasts out there who are less cack-handed than I am, take a good look at the BRAT.