If you're only carrying two weapons, one of them almost HAS to be normal typed damage. At the very least, both weapons must be of different damage types.

Strictly speaking, you're not using the Freezing Atomizer for damage output anyhow. The powerful part is the freeze status it inflicts, allowing you to outrun and outmaneuver monsters. In most cases, you can just freeze everything in place and let the rest of your group do the actual work of killing stuff while the freeze stops them from being mobbed.

If you're running solo, the Firey Atomizer might actually be a better option, as it can stack up quite a bit of damage once the enemies are burning. You just have to be careful not to set oilers on fire by accident.

Anyhow, as for a second(/third) weapon:

If you really like bombs that much, one of the Blast Bomb series is a good choice for putting the pain down. It's a bomb, it deals normal damage, and it has good knockback. What's not to like. If you're dead set on specific damage types, there isn't really a good direct-damage shadow or elemental bomb option, but the Spine Cone from Snarbolax tokens is a good option if you're going somewhere that piercing damage is going to work well.

Other options are a good sword or gun. I largely use Alchemers, as far as guns go, but they're all specialised damage types and aren't always a good solution to whatever problem you might run into. I'm not actually familiar with the normal-damage options you might have in Firearms, but I've heard lots of good things about the Magnus line, and the standard blaster line (from the quartermaster in Haven) is likely serviceable enough to pass muster.

Sword-wise, I'd personally look into the Calibur or Brandish line blades. Caliburs are a strong normal-damage option with a very useful charge attack. Brandishes break down into 2 elemental and 1 shadow damage line, for more specialised application. The Sealed Sword or Troika lines are also a good option. If you can stand the (lack of) speed, you might find that the knockback more than makes up for it. The Troika doesn't have a 5* upgrade right now though, so bear that in mind if you're making long-term plans.

As I mentioned, if you're only carrying one other weapon along with your freeze bomb, it should be a normal damage type. If, like me, you're carrying 3 weapons, I'd suggest carrying a weapon that's particularly effective on a type of enemy you find difficult to fight (either Snable Barb or Flourish is good idea for Wolver and/or Devilites, for instance), and a catch-all normal damage type in the third slot. I highly recommend at least one of your three weapons be a sword. Even if you prefer bombs or guns, swords are just too good not to have one on hand.

Between Archeron and Grand Faust: i have personally both and go currently with the Nightblade line. While the Grand Faust deals better damage with curse chance and offers knockback the swings are really slow and make you vulnerable to enemies for longer compared to the fast swings from Nightblade.
Between Flourish and Magnus: Magnus, now thats one awesome gun, each bullet knocks the enemy to the ground, it does wonders on the warping wolvers from Tier 3, sniping Wings with it is also excellent. You shot it while standing still, this might be a problem for the first few days as it was for me but its rather easy to get used. Since its Piercing damage you can use it also succesfully on Gremlin Menders, they'll be knocked back to the ground just like wolvers. Damage from it is generally high and the stun status is great to have as well.
I also love Flourish, its first swing is really, really awesome. I think its comparable with all heavy swords (i can open 4 boxes with flourish and 4 with faust). From those two i currently go with the Flourish as i got tired with guns, killing stuff with them takes too much time. But hey, if you want to take your time go with Magnus, its way more fun to play around with it, just frustrating when you start noticing how slow you are.