Well, I guess I'm boring. I've never done this. :)
I think "splatbooks" were big in 3.0 and 3.5 and I only played 3.0 for about 4 months. I guess I kinda missed this boat. (Thanks to the Dungeon Bastard I DO HAVE the "Horrifically Overpowered Feats" book...)
When I played Champions, I did enjoy incorporating Powers from Champions 2 and Champions 3 into the game. I remember I wanted to play a Gadgeteer with a gadget pool. That was kind of abusive.
I also knew how to make an Elemental Power Pool go a long, long way during character creation.