I've always felt that one of the best setups is a Siren with the Hellfire.
The Hellfire was one of the best setups for all classes. It's pretty much
the most overpowered weapon in BL1, no joke.

The Hunter was/is my fave class as well. Lilith 2nd, Roland 3rd, Brick 4th.
Something about the Hunter, where he could just kick butt with revolvers or snipers + if you got his SMG skill up it made a fine backup/alternative weapon. A good, fast, scoped masher revolver+his massive critical bonuses = super deadly. Could never get into Brick's melee, even tho it was powerful, but he could be silly fun with a Launcher (Helix or one of the orange ones) once you got ammo regen for it. Roland was kinda boring...especially if you played solo, like I did/do 95% of the time. Just a general all-purpose character with a turret. I'm hoping the new Commando/Axton will be more fun for solo.
It's one of the few games my spouse likes to replay repeatedly so I've played
a lot of Borderlands - we still play - tons of playthroughs with all characters multiple times. Mostly solo but sometimes co-op with hubs.