I'm aware that Tsubasa-no-Me has already suggested something along the lines of a sticky bomb (a bomb that attaches to foes which walk over it).
However, this is partly a cross between a bomb and a gun, taking its bonuses from gun trinkets rather than bomb trinkets.

Gooey Grenade Gun/Glue Bomb Launcher
Essentially, the attack launches a projectile that sticks to whatever it hits. The projectile flies over a limited distance; if it hits an enemy, it will stick to it, but if it doesn't hit anything and reaches the edge of its range, it will simply drop to the floor. (Hitting the wall will cause it to stick to the edge of the floor, for simplicity of graphical purposes.)
When the projectile hits, it does a small amount of normal damage (with a chance of minor stun on the original target due to the glue dripping over it?). Shortly after impact, the projectile will explode, dealing moderate damage in a radius around the target in a similar nature to a blast bomb. (Piercing damage from shrapnel of the exploding grenade? Alternatively elemental or normal, possibly chance of fire from flammable glue being ignited by the grenade.)
The gun would have a look similar to an IRL old-fashioned grenade launcher, with a clip of 2 and a 'no movement whilst firing' restriction similar to the Magnus line. The firing/reloading rate would be about that of the Magnus line as well (in order to prevent the gun from being OP, and having bombs flung everywhere really fast).
Standard shot has range of an alchemer-line gun, with speed of an equivalent level Blaster-line gun; charge deals higher damage and covers higher area upon explosion, as well as the projectile moving faster (midway between Blaster and Antigua) and having a further range.

'Affectionately known as the Triple G by those who use it, this gun gives a sticky end for those unfortunate enough to get within the grenade's blast radius.'

Any thoughts? o3o I've tried to keep the gun from being too powerful/weak, but let me know if there's something else you can think of.