Based off the Source engine Goat Racer is a vehicle combat gamemode for Garry's Mod. It's an arcade-style game in which you have to race to the finish first. You can do this by straight out racing or you could improve your chances by buying weapons and upgrading your vehicle. The action is high-paced, crazy and offers MORE then 6000 ability/upgrade/weapon/paintjob/vehicle combinations. If you're lucky you might find yourself firing a flack cannon from a Lamborghini at 300 MPH.
This is where you upgrade your car.
When you're ready to race, press F9 (I think it was) to get put in the queue.
You'll be waiting no more then 5 minutes though. That's the time of each high-paced race.
Notice the flying menu as well if you want to check out stats.