Ripper: Very nice damage, rather high ROF and ammo, with decent damage and range.
Photon Blaster: Probably better than the Vamp Charger, great ROF and range, great accuracy, but not as outstanding damage.
Terminator: IDK, it worked for me, it has an amazing range for a shotgun and it's lethal up close. I got the Zapper but it seems more like a close-range assault rifle feel.
Hailstorm: Probably the best. I don't have the Assault Bouncer, but from it's stats it's pretty bad, only benefits from Fire and Multi-Shot. The Hailstorm allows you to pretty much shoot enemies from around turns and on platforms - like in the Facility level, you can use the right jump pad to get the drop on any guys protecting the flag - just keep shooting while you're jumping near the top, it should hit them.
The Precision Laser is also worth checking out if you like to go for the head/crotch/butt.
Holy Grail: No doubt the best Sniper weapon. I one-shotted so many guys with this, plus the Fire attribute ensures death of the any Adrenaline-equipped enemies, like J. Rockit in the Alien Campaign.
Destroyer/Flame Thrower: IDK, the Flame Thrower inflicts self-damage, especially if you don't have that armor where you're invincible to fire damage. The Destroyer worked OK for me, but I just prefer to stick with other weapons.
Rocket Launcher: Yeah. The Ion Cannon doesn't deal as much damage, nor does it have the same amount of speed, the Grenade Launcher often won't detonate fast enough, the Ice Hunter deals too little damage and has too little ammo to be of much use, and the Acid Hound is sometimes just too expensive.
That's what I got, hope you think the same :)