Fantasy flight, Only War. With some things from the other systems mixed in, but only minor.
Fun as hell game, though all the other players were retired military, and im just a filthy civie. Still fun as hell, my dude was pretty much a warboy from madmax, and come to repair and driving rolls, the omnissiah loved his ass. Though tech priests hated him.
Feats include,
Repairing busted chainsword.
Repairing busted chimera that had been religated to source for scrap.
Hijacking a traitor chimera from the middle of their base.
Repairing a broken plasma gun tech priests had written off. (And of course, couldnt find any ammo for it beyond first plasma flask)
Repairing firing systems on a busted baneblade.
And... the crown jewel...
Repairing a 4000 year old broke. Power field shield device he found on a space hulk. Had several extras for parts and to study, best quality tools, and a very nice 001 on a d100. (Lower the roll the better)
GM was shocked, tech priests were amazed, magos blue screened. Good times. Good times.
One annoying thing was gm didnt beleive in giving people gear upgrades. So at one point we are fighting plague marines, and here is my dude with an empty plasmagun... and a shotgun. Against nurgled up marines in power armor.
Smaller threats it was effective, but moment theres decent armor... nope.
...
And i gotta go. Brain melting down, dumbass bitching that "people trying to do their jobs right is whats wrong with this economy!!".
This said to bus driver, who expected person to pay to get on the bus.