Thrash, right behind Battletech, is the system I have written the most crap for. Here it is (well, a little bit of it).
Demon's Spar
Pre: FOC5, Blades 2, STR6
Maneuvers: Power Blade (Extended Use), Blade Runner, Riposte, Slice
Upper, Spin Slash
Prerequisites: Focus 5, Blades skill (or equivalent) 2
Assassin's Path
Maneuvers: Backflip, Displacement, Backflip Kick, Multi-Kick,
Multi-Strike, Kippup
Prerequisites: Strength 6, Agility 9
Quote: "Hit fast, run faster."
Shoryuujin
Basic Maneuvers: Kippup, Power Block, Displacement, Backbreaker,
Choke Hold, Knee Strike, Backhand, Ear Pop, Elbow Strike, Knife Hand
Cost Modifiers: Only Musical Focus, Chi Blast, and Focus
Rage available from Focus
Quote: "Honor is a concept invented by fools."
And if you ever want to play a Thrash campaign about Jet Grind Radio or Jet Set Radio Future, here's something to get you started: JGR/JSRF Thrash Supplement. Beware, it's strictly bare-bones stuff.