Spheal, the Clap Pokémon. Spheal moves more quickly by rolling than by walking. They are sometimes known to cross oceans atop icebergs.
– Ash’s Pokedex
Spheal has a rather amusing design. It is a perfect ball, and in Pokemon XD, after it gets hit, it rolls back to its previous position.
One of its abilities, Ice Body is quite nice, restoring HP during Hail, which makes it useful on a water/ice team.