Spore - The Penis Monster Poke
Give boys the ability to create anything they want, and monsters with enormous cocks is what they'll produce first. We really don't need to say any more, just watch the video. It still cracks us up.
Metal Gear Solid - The Stairway Super Sprint
Despite being a series with some of the highest production values of any game, it seems Konami still hasn't quite grasped how to make they're super sneak man run and, even more noticeably, climb stairs properly. His legs motor away like pistons in an engine, and he looks like he's doing the doggy paddle. Skip to 5:30 in this video and watch him swim through a corridor and motor up a staircase in MGS2.