Personally prefer all classes to be viable. Though if you had a mechanism where you could feasibly change classes then making the harder to get ones be more powerful would probably be okay.
Very Pistol
A compact, cockpit optimised emergency signalling device. Or a flare gun. Your choice. Fires a 2 damage shot for 6AP at an accuracy of 3-17 and a crit of 5-15. Non-allied units facing the place the shot comes to rest take an AP penalty and will do their best to get away from the burny thing, which takes precedence over other things. Luckily for you, most people don't realise that the sheathed magnesium flare this thing fires is more likely to cause direct burns than actual ignition, seeing as it's mainly shell.
$Money
5AP shots: $Not as much money
Extra accuracy: $More money
Crit of 3-17: $Lots of money
Combat Shotgun
Quite a bit more efficient than your old hunting shotgun. Also accepts lots of types of rounds, though changing them on the go will be a bit of a problem (3AP action). Each shot only produces 6 .75 damage pellets, but only takes 5AP. It has a 4-16 accuracy and a 9-10 crit.
$Money
Slug rounds (changes to a single 3 damage shot with 3-17 accuracy): $Not as much money
Flechette rounds (changes to 15 0.5 damage pellets): $Not as much money
Dragon's breath rounds (changes to a small directional explosion much like the Claymore, 1.5 damage): $More money
Handy ammo slots (changing ammo type is a 1AP action, shots take 1AP less): $Lots of money
.600 Nitro Express Revolver
Because you want to shoot tanks with your side-arm. Each shot is a monstrous 3 damage round that takes 6AP to fire. If you were out of your freaking mind, you could theoretically fire it at 4AP per shot. Y'know - if you enjoy the sound your shoulder makes when it's dislocated and relocated (large self damage). Each shot has a hit chance of 3-17, a crit of 9-12, and reduced penalties to armour.
$350
No self damage, but -1AP penalty per turn: $100
Rapid shots are only 3AP: $150
Depleted uranium penetrators. Because you want to shoot at battleships with your sidearm (bullets penetrate small enemies and do extra damage to large ones; penetrating bullets become 5 0.5 damage pellets with a hit chance 5-15 and crit 10-10). : $250
Derringer
Why would you even want to buy this? 0.5 damage shots at 5AP each with 4-16 accuracy and 9-11 crits.
$Bloody Cheap
Less AP cost: $Medium expensive-ish
More Damage: $Medium expensive-ish
You get two shots: $Medium expensive-ish
.410 Breach Loader Shotgun
Don't be seen in public with this thing. It pretty much marks you as a newbie that can't handle the recoil of a real shotgun. Each shot is 5 0.5 damage pellets, at 6AP a shot. 4-16 accuracy and 10-10 crit.
$Cheap
Extra Accuracy: $Medium
Extra Pellets: $Medium
Double Barrel (Double pellets, +1AP a shot): $Expensive
Fast Loader Clips (-1AP each shot; also cancels penalty from double barrels): $Expensive
Carbine
Basically an automatic pistol with a stock. It'll have to work as your smg for now. 0.75 Damage shots at 2AP each. 5-14 Accuracy and 10-10 crit.
$Cheap
1.5AP Shots: $More Expensive
1 Damage Shots: $More Expensive
4-15 Accuracy: $Yet More Expensive
Vector
Like a submachine gun, but with more sliding blocks or whatever crap it was that makes this thing almost recoilless whilst keeping it a bullet hose. A 0.75 damage shots at 1AP each bullet hose. That has an accuracy of 3-18 accuracy and a 8-12 crit.
$Lots of money
1 Damage Bullets: $Not quite as much money
Less AP Cost: $More money
Halve AP Cost (Applied after less AP Cost): $Very, very large amount of money
DP Machine Gun
It's a machine gun, sure, but that giant disc on the top is going to be a pain to reload. 8AP gives you a decent 6 shots at 1.25 damage each with 4-16 accuracy and 9-12 crits, but moving in the same turn costs double AP.
$Cheapest machine gun
Extra shots: $Not quite as expensive
Less AP: $More expensive
No AP Penalties: $More expensive
BAR
Basically an automatic rifle rather than a machinegun, but at least it's pretty quick. 4AP gives you 3 shots at 1.25 damage with 5-15 accuracy and 9-11 crits.
$Marginally more expensive than the last machine gun
Extra shots: $Not quite as expensive
More Damage: $A bit more expensive
Less AP Costs: $More expensive
RPD
Not that great, but it's still better than that giant disc thing. 6AP Gives you 6 shots at 1.5 damage each with 3-17 accuracy and 8-12 crits, but moving in the same turn costs double AP.
$Fairly expensive
Extra shots: $Not quite as expensive
More damage: $More expensive
No AP Penalties: $More expensive
SAW
Decent machinegun that's nice and powerful without starting to get ridiculously heavy. 7AP gives you 8 shots at 1.5 damage each with 3-17 accuracy and 8-12 crits, but moving the same turn costs double AP.
$Really quite expensive
Extra shots: $Not quite as expensive
Lower AP Cost: $More expensive
No AP Penalties: $Much more expensive
Browning .50 Cal
This belongs on a turret, not in your hands, but if you insist. 8AP will give you 10 shots at 2 damage each with 4-17 accuracy and 8-11 crits, but moving in the same turn makes it 6-15 accuracy with 10-10 crits and costs twice as much AP. When not firing, you still take a penalty to movement to the tune of 1 extra spent AP every two steps.
$Holy balls this will be expensive
Extra shots: $Not quite as expensive
Lower AP Cost: $More expensive
Lower AP Penalties: $Much more expensive
XM214
It's a 'man portable' minigun. Hah. As ridiculously bulky as it is, two guys with a couple of these could turn any confined space into what equates to a meat grinder. Spinning up takes 4AP, and allows you to fire for that turn. Firing takes 2AP and fires 8 1.5 damage shots at 3-17 accuracy with 7-13 crits, and you can repeatedly fire as many times as long as you have AP. However, moving whilst spun up takes 2.5 times the AP and causes the gun to fire at 7-13 accuracy. Even when not firing, you will still take twice the AP to move.
$If a person with points in machinegunner gets this gun then the game is essentially over. Some ridiculous number goes here.
Increased spin up speed: $Mad
Fires 2 extra shots per 2AP: $Crazy
Strap two together (Double shots fired [applied last], moving takes 4 times AP spun up, 3 times at all time): $The players' total money, plus 10