I'd like to see some additional weapon selection in the Bomb category. As things currently stand, Swords are the most diverse grouping, even more so now that they've gotten a whole new tree, plus an expansion to an already existing tree. Guns are the next on the list, with all the flavors of Alchemer and the Antigua, Autogun, Blaster, and Magnus lines. Bombs, however, have the most limited options and the most lackluster selection:

The Nitronome - Don't pretend that there are any other types of high end blast bomb out there. The other ones are pitiful in comparison to the speed, size, and comparative power of the Nitronome.

The Elemental Haze Bombs - The Fire and Ice ones seem to have the most promise, though the poison one surely has its uses. Decent line.

The Graviton Vortex - Kinda nice that it pulls the enemy together, but the secondary blast defeats this purpose, and enemies are still free to attack from its confines. Doesn't last long enough to make it truly worth it, and the slowed down walking speed makes it very chancy to use. Not that great.

The Crystal Bombs - Only bomb that doesn't have a circular effect. Could be useful, but only goes to 4* and I don't find myself very interested in it. Could be possible to get multiple hits with it, but that seems to be a hit-or-miss possibility. With no real knockback, it doesnt really compare to the Nitronome.

However, I do have some ideas that could breathe some fresh life into this set of weaponry. And I'm not saying make more of the same; I'm suggesting adding new utility and tactics to the bombs. For Example:

Cluster Bombs - Much like how the slimes blow up, only you get to place them at will. Could add some elemental effects for the secondary explosions. I would expect more projectiles at higher star ratings, and maybe slightly higher blast radii. Small blast for initial explosion.

Turrets - Who wouldn't love to have a placeable turret, possible source of piercing damage again, or maybe flamethrowers? Needs a decent duration to make it viable, but a longer charge time would make it harder to chain lots of them together.

Rocket Launcher - Who says it needs to be placed? Since bombs are Charged attack only, why not have a chargeable rocket that you can fire at your foes?

Mines - The gremlins get to toss mines, so why can't we? Allows a Faster Attack Rate bomb to actually be a viable option, and a charged attack could cause a cluster to drop. I would expect smaller damage numbers on average to make up for the frequency of attacks.

Claymore mine - How about a bomb with a directed explosion? Give it stronger knockback, and you direct its cone of fire based on where you point yourself. Possible wider cone or longer range as the Star rating goes up.

These are just a few ideas that come to mind; plus, the programming for some of these effects may already exist in part, making it less difficult to implement a player-based version.