Big Al, the largest alligator in captivity in Texas. He's over 13 feet long and weighs almost half a ton. I'd like to ride him.
A tortoise from the same place. I'd also like to ride this guy.
Or this one (the tortoise, not Atreyu).
UPDATE (for Woahbajeez)
The largest tortoise in the world is the Galápagos tortoise. There isn't an actual record for the one current largest (that I could find). The largest turtle ever found (dead, unfortunately) was a leatherback that was found washed ashore on Harlech Beach in Gwynedd, Wales. As for the largest living turtle currently living, no idea.