Description This was interesting to play around with. No, that's not sarcasm, that's seriousness. Really!
Well, OK, it wasn't really fun on it's own. What makes it fun is how it affects navigation over the various maps out there. Basically, the JumpGun is a portable jump pad. There's also a built-in superpowered forward dodge move, but... who really needs to use super forward dodges? Maybe when crossing the occasional canyon, sure, but not a lot of maps even have canyons....
Anyway, why is this fun, you ask? It drastically alters the way you have to perceive the game, that's why. Previously inaccessible areas can now be accessed with impunity. Other tricky areas are now much easier to access. There are many more viable sniper nests. It really forces you to think outside the box and rework your tactics, since it opens the way for dozens of new play styles.
Sadly, it can't be added into normal spawn rotation via mutator, and has to be spawned via console. However, it could easily be implemented into custom maps. Would be nice to have it added into standard gameplay, though.
Also, it uses the shield gun model, rather than it's own unique model. But, modelling isn't particularly easy, so that can be forgiven.