Here are some variations for different versions of Tunnel Goons.
Skill System: Replace the three main attributes with specific skills, 24xx style. You could have sword fighting, crossbow shooting, acrobatics, sneaking, or anything else players can come up with.
Hits: Instead of rolling for combat, deterministic damage is exchanged. The damage is 1 plus any skill bonuses or advantages.
Maneuvers: If you want to do a combat maneuver, you can do so at the cost of any damage you would do. If you end up not doing damage in combat, the maneuver fails.
Static DS: Make every DS a 10.
Micro-combat: Zoom in on specific combat maneuvers to focus in on the action. Go for a stab, attempt to parry, and go frame-by-frame. Keep track of pinned limbs, positioning, etc.