In 2013, Audi UK put together a commercial featuring two of their RS 4 Avant Station Wagons outfitted with paintball guns
and competing one-on-one inside a large commercial airplane hangar.


The commercial starts out with a brief montage of the cars being outfitted. Most prominently, each features a huge cannon mounted on the hood,
mocked up to look like a Browning M2 .50 caliber machine gun, probably just to make the paintball guns look large and impressive. Note the
top-mounted Empire Halo Too electronic loader.


Each car is also apparently fitted with an "oil slick" spray mechanism- shown here being filled with a thick paint. The black car uses blue paint,
while the white car uses yellow.


A nice close-up of the  Halo Too being loaded with paintballs.


This is the only scene, even in the "making of" video, that even hints at the actual marker inside the dummy M2 housing.
It's not at all clear, but the faint hint of Picatinny rails makes me think it's a Smart Parts SP1, although that's just a guess.


The markers are almost certainly electric, fired from inside the car using this big red button (and apparently a badly-fitted driving glove.)


The drivers get a quick try at a target- note the indicator light on the Halo Too as the gun and loader cycle.


And it's time to face off. The cars start back-to-back, and run to each end where some boxes have been set up as barricades.


The black driver loops around his bunkers, while the white driver takes cover.


The bunker, however, isn't big enough to cover the entire car, so the black driver takes his shots...


And scores the first couple hits of the game!


The two drivers then try to jockey for position, drifting and sliding, getting in quite a few good hits at times.


The scores are mostly even as the black car gets into position...


... And tries out it's "oil slick" sprayers.


The sprayers leave two long streaks of thick paint...


... Which causes the white driver to skid momentarily out of control.


The white driver retaliates by tossing out a grenade- burning fuse and all. I suppose he lit it with the cigarrette lighter. 
(Filmed in the UK, so the cars are right-hand-drive.)


Well-timed, the grenade detonates just as the black car passes...


... And quite spectacularly too....


... Thoroughly coating the black car and putting the white driver well into the lead.


Both cars are well-peppered at this point, and the white driver leads his opponent right past a booby-trapped barricade.


The black driver strikes the bunker, dumping gallons of yellow paint all over his car.


Which nearly triples the white drivers' score....


And gives him a Knockout score!


The game then enters a bonus round, which is somewhow scored by... driving through puddles of paint dumped on the floor. 


And drifting. Apparently lots of drifting. 


And the white driver wins, 2241 to 724!