In theory, each custom car is "one-of-a-kind" in its own right. That doesn't excactly fall under the "one-off" category. A one-off is a completely custom-built car of which only one of that actual car exists in the world. A Camaro with a mohawk and color-changing wheels is unique, but a Camaro is not a one-off. That's why this past month was so exciting. A ton of actual one-offs popped up, including the incredibly rare McLaren X-1, a ridiculously awesome dump truck, and a campter COE. Check out the impressive work in The 15 Best Custom Cars of April 2013.