A lot of the games mentioned in this thread are not rare at all, Paper Mario isn't rare in the slightest, and neither is Eternal Darkness.
Gotcha Force. Now that is rare. Its a great game, but because it wasn't a known franchise or a sequel it was undesrvedly treated badly in reviews.
The GC versions of Second Sight, Timesplitters 3, and SSX 3 are rare too.