Game Cube worked in 2x2 blocks of pixels and could also run primitive "shaders" by cycling a pixel block through the pipeline multiple times with different settings. Made for some nice bump mapping demos but I'm not sure how much it was used in practice.
I've always been kind of fascinated by the state of GPUs immediately prior to fully-programmable shaders becoming the norm. It particularly comes up in the world of emulation, where often those weird fixed-function pipelines were abused in interesting ways to produce particular effects, and now someone has to figure out how to write a shader for a modern GPU that can perfectly replicate what that old pipeline block used to do, including all the edge-cases around overflow, saturation, and so on.
Unfortunately the inline demos seem to now be broken, but I found this article a fascinating treatise on how Gamecube and Wii games do things like render water:
