You can see yourself by going to http://pokemondb.net/move/all and choosing a type from the menu, then clicking to sort the column. But I will summarize anyway...
NORMAL - Explosion
FIRE - V-Create (or Blast Burn for a move more Pokemon can use)
WATER - Hydro Cannon
ELECTRIC - Lightning Strike (or, Zap Cannon/Thunder/Volt Tackle for more Pokemon)
GRASS - Frenzy Plant
ICE - Freeze Shock/Ice burn (or Blizzard for more Pokemon)
FIGHTING - Focus Punch
POISON - Gunk Shot
GROUND - Earthquake
FLYING - Sky Attack
PSYCHIC - Psycho Boost
BUG - Megahorn
ROCK - Rock Wrecker/Head Smash
GHOST - Shadow Force
DRAGON - Roar of Time
DARK - Foul Play
STEEL - Doom Desire
Remember these are the most powerful only, not the actual best moves. For example Frenzy Plant stops you from moving the next turn so it's not a good move at all.