Signature moves?

It's kinda hard to choose, and even though it's a good thing that these moves are available to more than just these Pokémon, I think Drill Run is just especially suited for Excadrill, and Defense Curl for Sandslash given that some of its Pokédex entries specifically mention that it curls into a ball to protect itself.

 

Oh right, Fury Swipes. Yeah, that would certainly suit him as a signature. So would Slash, hell, it's in his name. But I suppose it's a pretty basic and common normal contact move and not really good for a signature.

 

Rollout for a geodude seems pretty obvious. Dig for diglett, head smash for rampardos...

 

Hydro Pump for Blastoise.

 

Crush Claw for Zangoose, Dragon Rush for Garchomp and perhaps Supersonic for Zubat?

 

Minimize and Muk.
Painful memories of that one trainer in R/B/Y

 

Speaking of Muk, Sludge Wave would be a decent signature move for it. Because Muk is, you know...a wave of sludge.

 

Mega Punch sounds like a hitmonchan thing. and Mega kick HItmonlee.

 

Thunder for Thundurus. Rain Dance for Thundurus too.

 

Leaf Blade for Snivy and Serperior, Solar Beam for Servine. Always results in a one-hit-KO.

 

Uh..no, it doesn't. Even in-game battles it's not an assured OHKO, unless you are fighting Pokémon way weaker than you. Good moves sure but that's overrating them just a little bit.

 

Sing for Jigglypuff, obviously. Helping hand would probably work for Plusle and Minun. Maybe attract for Lopunny? Mean Look for Gengar.

 

Volt Switch for Rotom. Hopping around those electronics all day. [:

 

Psycho Cut for Gallade, I'd think.

 

Aqua Jet for Buizel/Floatzel

 

Blaze Kick,Muddy Water, and leaf blade are definitely the Hoenn Starters Signature Moves

 

Bite for Mawile.

 

I'd say payback for umbreon, night slash for absol and ice shard for cloyster. I think they'd definitely would make good signature moves for those three.