I'm listening to a podcast at the moment, and the people on the podcast were discussing their favorite controllers. Someone mentioned the Pippin controller and stated that he liked the trackball on it. I got to thinking why exactly trackballs didn't really catch on. I mean, sure, they don't exactly have a place in modern gaming (because that'd be akin to using a ball mouse), but I'm curious as to why trackballs weren't initially widely used. Sure, the analog stick is arguably more versatile, but it would've been nice to see trackballs on more controllers and for trackballs to gradually transition to touch pads or something comparable. For first-person shooters, this would essentially give players the same level of viewpoint control that PC gamers have with mice, and it's not as though you couldn't still have analog sticks for movement or something. I, personally, would rather have a d-pad for movement and a trackball or something for looking.
1st Edit: Holy shit...somebody actually makes these for Xbox 360. - Link
2nd Edit: Bah, apparently, it needs to be individually calibrated for each game, and it's still not gonna give you all of the capabilities that you'd have with a mouse and keyboard setup on PC. Since most console games don't actually support mouse input, this thing's really only translating the input data to whatever you'd experience with an analog stick. That does make it more accurate, but you won't be doing quick 180° turns with this thing.