Nightwing's Vehicle

Nighting's Vehicle is a jet-ski that Nightwing drives. In Episode 7: Nightwing Returns, it's revealed that it has a cloaking device that Nightwing brought. Nightwing might've built it or brought it himself, saying "Oh, that's my car that I got after I got some money." After Nightwing knocked himself out, Batman claimed that he owned the car, as Robin says "Yay! My very own jet ski!" to Batman as he showed Robin different cars (including Robin's former vehicle).

Vehicle Biography
The jet ski (which is what Nightwing's vehicle is) was seen twice in it's list of appearances. It has appeared in the episode The Side-Car and the Lego Batman, Spider-Man, and Chewbacca Movie. It might be a back-up vehicle, like the The Side-Car.

Trivia

 * The vehicle might've been built for Nightwing's personal use, as it only has one seat, as revealed in the Lego Batman, Spider-Man, and Chewbacca Movie.
 * Batman was extremely jealous of Nightwing's vehicle, as shown in episode 7, hence why he claims he owned it after Nightwing knocked himself out.