The OP already covered this, but Lanturn is a totally underrated Pokemon. Good special bulk, BoltBeam resist (fuck Magneton), Volt Absorb, incredible synergy with things such as Cloyster, Gyarados, Vaporeon, Aerodactyl, Skarmory. It struggles against physical threats (though it can switch in on Banded HP Flyings), is walled by Celebi, and is easily revenged by Dugtrio, and has only Rest for recovery, which really lets it down. But aside from those minutiae, Lanturn is far from outclassed in OU, and can wall the vast majority of Waters in the tier (exceptions being Gyarados and Swampert, who Lanturn can still piss off with a well timed Toxic). While it can't switch into Gyara, it certainly stops it from switching in, and if you can predict well, CB Mence and Aero shouldn't cause too much problems. Really good at luring them in too, so you can catch them with a Thunder Wave/bolt. Often I've found that, Celebi withstanding, the opponent simply doesn't have a safe switch in to Lanturn.