TM 22 Solarbeam just cause it's one of my fave moves :D
I also like Toxic, Aerial Ace, Psychic and Earthquake, the latter of which because it meant I could evolve my Rhydon earlier and teach it to it instead of waiting to learn it lol
Hon. mention to Shadow Ball, Ice Beam, Giga Drain and Dig
HM-wise I quite like Waterfall, I think it's pretty Also liked the introduction of Dive, that was pretty neat outside of battle.