Yes, yes, I know it's redundant. Anyway, these will be bombs specifically tailored to certain niches- or just really cool ones.
Tropical Storm
(2* Wave Bomb -> 3* Wave Bomb Mk II -> 4* Wave Blast -> 5* Tropical Storm)
Tropical Storm's blast radius isn't your typical circle. It starts with a tiny circular blast, then creates a wave that spreads forward in an arc in the direction the bomber was facing. The wave stops at low walls, and anything it hits will be slammed with high knockback and Elemental damage. The range of the wave and the length of the arc relative to the initial blast gets higher as the bomb is upgraded (with the 5* reaching 6.5 squares and having a 90-degree arc).
But the best part? Nobody will know which way the wave will go unless they see the direction the bomber's facing, the wave travels quickly, and the fuse time is short. The range of the wave is close to a short-ranged gun, though the wave will not pass over walls (don't want to make gunners too angry). The charge time is the equivalent of the blast bomb. In addition to being a good Slag-flooder in Legion of Almire and an excellent circuit breaker in GitM, the Tropical Storm will tear up Skolvers that don't see the wave coming. A quick-turning bomber will be able to baffle any Skolver.
Flavor text:
2*: "A bomb that creates a wave of water specifically tailored to fry circuits and wash away the undead."
3*: "Addition of a simple seismic mechanism has increased the power of the Wave Bomb considerably."
4*: "Improving the seismic mechanism took a single lot of Ironwood and a whole lot of testing. Fortunately, those Shufflebots were not destroyed in vain."
5*: "At the end of a storm, normally one will find loads and loads of robots with short circuits. That was basically the general concept of this bomb."
Lethal Urchin
(2* Urchin -> 3* Sharpened Urchin -> 4* Toxic Urchin -> 5* Lethal Urchin)
The Urchin is a "bomb", in the loosest sense of the word; it's closer to a bomb than it is to a sword or gun. Basically, it's a metal ball with chrome spines; the later versions have them dripping with poison.
Its unique feature is the amount of ways it can damage a foe. Lifting an Urchin happens quickly, but will smack enemies in front of the bomber for a small (like, 5% of a same-level Spine Cone) amount of Piercing damage. Once it's charged (which doesn't take long) and laid down, it will immediately be able to poke anything that walks over it for the same minute piercing damage before it explodes. Once the fuse is done, the Urchin shoots out its spikes, turning into a temporary floor hazard! The Lethal Urchin has a range .5 spaces smaller than the Dark Retribution. Anything that walks on an Urchin takes gradual Piercing damage, much like the Dark Retribution.
Now, obviously, this has one specific purpose: GREAVERS! The Urchin will interrupt Greavers very effectively even if you forgot to charge it. It'l also be nice for Trojans; Urchin, half-circle, repeat will be very effective. It's not really a Lockdown bomb, but could be useful as an alternative to the VT (less range, but it can't be UV'd against quite as effectively). Devilites won't be too scared of it, but that's what you brought DBB for, right?
Flavor text:
2*: "An experimental Spiral Knight weapon, the Urchin is a useful tool for the gullible monsters of the Clockworks."
3*: "Many bombers that use this weapon often have come to the educated conclusion that, contrary to what some villains say, good will triumph because evil is dumb."
4*: "This Urchin has had a large amount of toxins added to its spines, but at the end of the day, it's still the same spiked trap we all have come to know."
5*: "Trapping's a good job, mate. It's challenging work, out of doors, and you won't go hungry, because at the end of the day, long as there's people left on Cradle, everyone's gonna want Greavers dead."
Antimatter Tempest
(2* Antimatter Spray -> 3* Antimatter Spray Mk II -> 4* Antimatter Storm -> 5* Antimatter Tempest)
This powerful Shadow-damage bomb has a small, practically useless initial blast. Then it turns around and drops anti-matter meteors on targets. The three targets closest to the bomb will have the meteors fall on their heads (with meteors that don't find a target simply dropping randomly near the bomb). The meteors can target objects up to eight spaces away (with the 5*; the 2* can only reach five spaces). The number of meteors increases by 1 for each upgrade, with the Tempest having SIX meteors dropped.
The meteors themselves rarely, if ever, overlap, so the damage is good- just barely below a same-level Nitro. The blast radius of each meteor is around 2-3 spaces. And the best part? The fuse time is short. Hope you swordsmen brought your Snarby coats, heh heh heh.
Flavor Text:
2*: "A powerful weapon capable of weaponizing anti-matter. This is an experimental version."
3*: "The only disadvantage to this bomb lies in the fact that the jellies it kills are not safe to eat. Trust us on this one."
4*: "Ever had a problem with difficult people? A meteor to the face works wonders."
5*: "The Antimatter Tempest was originally going to drop twelve meteors, but the amount had to be cut in half to prevent friendly fire. Also, swordsmen and gunslingers would have been jealous."
Compliments? Suggestions? Scathing rebukes?
Tropical Storm takes advantage of the fact that bombs are actually directional without just making it a Brandish charge while retaining a radiating effect; the initial explosion still has the area of effect, but then the real show starts.
Lethal Urchin has a lot of utility with pierce damage, creating a rival for Barrage; do you want the large area and damage or small rapid attacks in a smaller area? It may not be a replacement for the old shard bombs but it creates a new mechanic to deal with a common problem for bombers.
Antimatter Tempest seems like Retribution with a more random based attack, though the homing radius is a little too far. If we go by the 2* having three meteors and every upgrade gaining one more meteor, the meteors could start around two spaces away from the epicenter equally apart from each other then fire away from the epicenter for one space (deals more damage before it hits the ground), then creates a tremor from the impact which travels two spaces further from the epicenter (less damage than the meteor crashing, but still fast and travels relatively far). Having the ability to track without the player doing anything just seems too powerful, not that bombers are undeserving, but then gunners would be asking for a homing bullet gun to snipe with.