When a weapon reaches V5, it will evolve. Here is what each weapon evolves into:

Shock blaster-Shock Cannon
Nitro Launcher-Nitro Eruptor
Plasma Whip-Quantum Whip
N60 Storm-N90 Hurricane
Infector-Infecto-bomb
Suck Cannon-Vortex Cannon
Spitting Hydra-Tempest
Agents of Doom-Agents of Dread
Flux Rifle-Splitter Rifle
Annhilator-Decimator
Rift Inducer-Rift Ripper
Disc Blade Gun-Multi Disc Blade Gun
Holo Shield Glove-Ultrashield Launcher
Qwack-O-Ray-Qwack-O-Blitzer
RY3NO-Rynocirator
Miniturret Glove-Megaturret Glove
Lava Gun-Liquid Nitrogen Gun
Bouncer-Heavy Bouncer
Plasma Coil-Plasma Storm
Shield Charger-Tesla Barrier