Multiple suggestions,
wingsuit -
Let's you travel further, faster, and replaces your parachute if you select it, however, your easier to shoot down from directly below and take impact damage due to the increaseed speed.

Sword/Shield -
Nothing to really say, sword is a 1 hit, shield blocks bullets but is about chest size. Has its own class with perks including speed blitz, where you live faster while running in a straight line. Guardian, where your shield is larger but your sword is smaller. And lastly, Ironclad, where you take 25% less damage from bullets. Sword nor shield have attachments of course. Possibly an achievement for killing 3 enemies with one slash of your sword, called brute force. Would be awesome to be a knight even if it's unlikely.

Motorcycle -
Same as an ATV but faster and easier to turn, however it only has 1 seat and flips easy