Hmm... I'm not so sure recoil is entirely a bad thing.
In a game like [T-word game here], I can understand where recoil can upset the game balance. But at the same time, a little bit of recoil adds a
lot to the game's immersion, even if it's so little that it really isn't noticeable on most weapons.
If you stand still and aim at the same spot on a wall and empty an entire magazine, you'd expect a decent game to at least bounce your crosshair a little bit for as long as you're firing, if not actually change your aim.
Take Crysis 3 for example:
http://www.youtube.com/watch?feature=player_detailpage&v=M9yTFN4uMas#t=99sMost weapons in the game will leave center while you're firing them continuously, but will return to zero when you stop.
Even if you were to include very minimal recoil like that to the point where it's barely noticeable, I'd be happier with it than with unrealistic no-movement clip emptying. It kind of makes a game feel more 'genuine' and gives it a higher quality feel.
On a separate note, I've got a few ideas floating around for how some of the guns could potentially look in a late 21st~22nd century era, or at least a few starting points for designing them.
For the shotgun, I think the ever-popular UTS-15 is a good sci-fi starting point for a shotgun, because of it's rugged, technically complicated look:

I'm thinking if one of your artists extended the length of it slightly in a rendition, added an 8-round clip for some futuristic 10-cm long cartridges, and possibly some color to whatever they come up with, it could serve as inspiration for this game.
I also had some ideas for the energy weapons of the game...
Large, high power industrial lasers commonly use a cylindrical crystal to focus the light given off by a light "pump".

In my mind, a laser gun would have a tubular emitter end around 6~10cm in diameter to house a laser crystal and a light source as well as various focusing elements. This would most likely have some means of cooling, like liquid cooling tubes leading back to the 'reciever' area. Towards the stock end, probably some sort of fixed stock with perhaps a holographic diagnostic display/round counter? The main 'reciever' area of the gun would likely house battery cartridges that could load either traditionally up into the bottom of the gun, or perhaps horizontally into the top? It would also have to house a small protected radiator if the emitter of the gun was liquid cooled.
A hypothetical microwave cannon would use a
klystron tube to create and direct microwave energy towards it's target. A klystron gun might have similar proportions to the above laser gun, but since this particular one is going to have a permanent battery, it will likely have a fairly large heat sink above or around the 'receiver' area surrounding the battery to dissipate heat.

(^ various heat sinks)
A Railgun will probably be loads of fun for the artists on the team.
Railguns use the magnetic force caused by the movement of electricity through a conductive projectile that is placed between two parallel rails to accelerate it to high speeds.
http://www.youtube.com/watch?v=C6cV10QEGGkI actually have sketched plans for a real world portable railgun that I never got to build due to financial limits if you think they might be useful.
Keep in mind, I'm just trying to throw out as many ideas and technical details as I can to try and help the artists.