The DLC-$$ is a vehicle in RCR. The car is based on the Delorean DMC-12 from "Back to the Future". It can time travel using a Flux Combobulator. It is used on some missions.It shots fire ou of the back if at the required speed (it also happens when you hit it).
The name is meant not only model 'DMC-12' but also to mock how game company con players with paid DLC.