If it's speed you're after, the Arrma 3s lineup is pretty quick. If you have more in the budget, the 6s and 8s lineup is good too.
But it sounds like you might be looking for a kit. And since you want speed, that rules out rock crawlers.
If you go to Tower Hobbies and click Shop>>Cars and Trucks>>By Competition Level>>Kits you will find some of the available kits out there. But my pick for a fast truck kit would definitely, 100% be the Tekno MT410. If you want a Short Course truck, Tekno has one of those too.
You have to take into consideration these kits require not only a battery and charger, but a motor and ESC, and a transmitter/receiver and servo.
What is your budget?