Spiral detonator
A single shot gun with interesting bullet mechanics. (don't worry the reload is fast)
It comes in 3, 4, and 5 star variants
The single bullet is about the size, and speed of a catalyzer bullet and does more damage than a magnus bullet (the range is 1 block further than the Antigua charge). The player cannot fire another detonator bullet till the other is gone. If the player fires while their detonator bullet is still existant then that bullet will explode dealing high damage, knockback, and possibly stun (lower than rigadoon chance) (instead of gun fire animation the /point emote is used for detonation). The explosion radius is comparable to blast bombs. If a bullet makes enemy contact before being detonated the bullet deals high damage (though less than a detonated bullet) and knockback/flinch rate the same as Catalyzer bullets (i.e. none).
Edit: blast radius reduced
3 star gun has blast radius of 1 star blast bomb.
4 star gun has blast radius of 2 star blast bomb.
5 star gun has blast radius of 3 star blast bomb.
The damage of each blast is slightly less than the damage of the blast bomb that is on their level. (5 Star gun deals slightly less damage than Nitronome but has knockback and blast radius of 4 star blast bomb)
The standard gun is Normal/Stun damage (stun chance is higher for the standard but other variants still have a low stun chance), there are 3 variants that are 5 star guns. (all have moderate status)
Shadow/fire (dark combustion)
Elemental/freeze (flash freeze)
Pierce/poison (toxic blast)
Edit: The charge attack is comparable to the Valiance in that it is larger and deals more damage. The mechanics of the charge bullet follow that of the standard bullets and are detonated in the same way. If they are not detonated and make enemy contact they still deal more damage just with no status chance.
Idea was based upon https://wiki.teamfortress.com/wiki/Detonator
I think this gun is helpful and reasonably powerful.