My favorite one must be Boo, the miniature giant space hamster. It's hard to describe why exactly Boo is my favorite. I think it's because it's such a charismatic creature. Just like Drizzt Do'Urden wields his Frostbrand and Defender scimitars, and Icewind Dale II's pre-generated Half-Orc Oaglata packs her unique Dead Cat Snack, Minsc carries his very own unique item: the amiable but further useless animal companion Boo.

Does Nanaki from FFVII count. If so then him. If not then my puppy from Fable 2. He was pretty useless in combat but c'mon! He could do back-flips for crying out loud!