Lamp!

The limbs are parented and pivot points at where they logically should be on a lamp. 

Post 1: Sketches

I don't have a scanner at home and used my camera to take these. Sorry for the bad quality. 

The first is a robo  sheriff. When it walks, its entire hip rotate 360 degree. Its leg cannot bent.

Animation wise, it should be the simplest.

The next one is a TVdoggie. It should be easy to model but animating 4 walking limbs will be a bit hard.

This one is a bit not original and probably quite hard to model.

A transforming bipedal motorcycle robot. Not the most original idea.

A combat walker. Again not very original but probably simple to model.