Actually, calling it an action figure does it a bit of a disservice. The term "action figure" conjures all sorts of images, mostly of very small men. This custom Strider from the Half-Life universe is not very small at all.
Not only does it look awesome, but its builder, nomadamusic, says it was almost entirely made from scratch, and even includes a few points of articulation.
Who needs large toy companies when individual artists can make their own Striders? Not nomadamusic, that's for damn sure.
Half Life 2 Strider Combine Custom Action Figure [FigureRealm, via Toycutter]