I'd argue it has an amazing move pool: Earthquake, Return, Brick Break, Rock Slide, Shadow Ball, all the elemental punches, Flamethrower, Ice Beam, Thunderbolt, Fire Blast, Blizzard, Thunder, Bulk Up, and in later generations it can get moves like Night Slash, Play Rough, Gunk Shot, Shadow Claw, Sucker Punch, and Focus Blast. Slaking has an exceptional selection of moves, and it's very versatile. It's ability is a huge hindrance, but if you use it as a hit-and-run attacker, switching it out on Truant turns and hitting hard when it comes back in, it will be incredible. If you're playing against your friends they'll be able to take better advantage of it and will either hit you while you're loafing around, or read the switch and be able to boost for free. In games, though, it's a phenomenal choice.