Watch Dogs 2 has some unique and interesting vehicles lying around the map. What's more, you can have it for free given you know where to find them and that you have superb stealth skills to steal them. Here's a list of these unique vehicles:

The Dangerzone

This Watch Dogs 2 sports car can be found by at the SVNR building which is located at a block near the Nudle HQ. Look for a small grate and use your RV to jump over it and into a 4X4 vehicle. Use it and reverse drive to destroy the wooden panel where you can find a hack box. Use your RV to hack it to open the garage door. Get inside and walk straight into the last door to get the Dangerzone.

Rainbow Missile

The Rainbow Missile is a motorcycle which you can find at San Mateo. Once you're there, enter aa restricted garden where the red bike is. Knock the guard unconscious with your stun gun, hack the gate to open it, and ride away on the bike.

Ice Cube

This is another sports car found in Kirby Grove in Watch Dogs 2. You can either drive or fast track through a Motocross rally. There's a dirt road to the left of Kirby Road, just follow it to find the Ice Cube waiting for you.

Danger Mobile

This green smoke spewing service vehicle can be found in the Yerba Buena Island. You can find it between an H-shaped building.

Flip Wagon

You can get this Watch Dogs 2 camper van by heading north to the Painted Ladies. After that, go down an alley and you can find the van on your right.

Mountain King

Mountain King is an off-road Watch Dogs 2 vehicle in Oakland to the right of Lakeside Park near your headquarters. Look for an Auto Repair shop where a forklift truck is sitting outside. You will find the Mountain King on a ramp behind a gated ramp.

Wrecker

Another Watch Dogs 2 vehicle in Oakland, specifically at the Port of Oakland. Head towards a forklift where you can see a bunch of containers beside it. Hack the camera near it to find which container this muscle car is in. It's in an open container at the top pile. Hack it and drive away.