There was a time, in the early 2000's, when I made an effort to buy anything by Rare. It started with Donkey Kong Country but exploded with my love for Banjo Kazooie and Banjo Tooie. Back then I didn't really have cable or the internet so I was never sure which games were out or coming out; I just looked for that golden "R".
While I've always loved Rare, Sonic Team is by far my favorite (at least they were during the Saturn/Dreamcast/Gamecube years). Their games were goofy, slightly cheezy, incredible fun, and reeked of charm. Sonic Adventure, Phantasy Star Online, NiGHTS, Burning Rangers, Samba de Amigo, Chu Chu Rocket, and Billy Hatcher!
Unfortunately, both Rare and Sonic Team got into a horrible lull in recent years, and while Rare is still doomed, Sonic Team seems to be catching a break with games like Sonic Colors, Sonic Generations, and hopefully the upcoming Sonic: Lost World. Now if only they could make something besides Sonic... :)
Anybody have any favorite development teams that they just Looooooooooooooove?