thunder - 120 power, 70 accuracy, 30% paralyze. hits pokemon using fly for double damage, and never misses in rain. use in the uber metagame, to kill kyogres. otherwise, thunderbolt is better.
fire blast - 120 power, 85 accuracy, 10% burn. actually worth using on a) anything that gets STAB on it, and b) physical sweepers, to deal with skarm/forry/steelix. use FB on sweepers, and flamethrower on tankish pokes, or if you need the extra PP.
solarbeam - 120 power, 100 accuracy, attacks on second turn unless it's sunny. half power in rain. use on exeggutor, but not much else. never use without sunny day, and a chlorophyll pokemon.
blizzard - 120 power, 70 accuracy, never misses in hail and hits both opponents in double battle. do not use, ever.