Intro: K'nex R2-D2
Sorry it has taken me months on end to publish this but I haven't been to my grandma's house lately(which is about the only place I can publish stuff!). Anyways, this is R2-D2 from the star wars franchise. He has the orange pieces just for the purpose of remaining in the standing position (otherwise he would do the splits!)
Step 1: The Garbage Can
Step 2: The Motor Assembly
Step 3: The Face
Step 4: The Legs
Step 5: How to Change Positions
He stands this way by a matter of balance
He can fly if you have a book of incantations.
Step 6: Next...
Generations Lugnut as suggested by ismith25
Fall of Cybertron Bruticus as suggested by stonegill