You ever heard of Super Crate Box? No? Go play it, it's free and fun.
For those who don't want to do some research, here's a list of the weapons and what they do.
Crate: Not a weapon. Gives you a random item when picked up. (Preferences that default to these weapons, but can have other items added?)
Pistol: It's a pistol. Shoots a single bullet, slowly.
Machine gun: Fires a lot of bullets. A lot of bullets.
Shotgun: It's a shotgun. It fires a bunch of bullets that vanish soon after being fired (about 8 bricks would be accurate to the game). Very close range weapon, very powerful.
Bazooka: It fires an exploding rocket.
Dual pistols: There's two pistols. They fire in opposite directions. (In 3D, they should probably not fire in opposite directions but rather in a V shape. Just... Because it's hard to aim sideways.)
Revolver: It's a pistol that doesn't suck. Bullet is twice as big and more powerful.
Flamethrower: It fires flames that stick to surfaces and burn for a while.
Disc Gun: It fires a flashing disc, which bounces once and then vanishes the next time it hits a wall. (Should only fire horizontally, otherwise it'd be too weird to use.) This disc is incredibly powerful and cuts through anything it hits without stopping aside from walls, but will often come back and kill the owner. (Note: In Nuclear Throne, it bounces multiple times, and Nuclear Throne is top-down and so would probably be the better example. Maybe make the number of bounces a preference?)
Mines: They're mines. You put them on the ground and then they arm themselves, then they go boom.
Minigun: It's... Oh, you have to see this one to believe it. The description is "This one has a bit of knockback." You can PIN YOURSELF TO THE WALL with this thing and slooooooowly slide down as you fire map-covering destruction that is just insane. It's got a huge spread (between 22.5 and 11.25 degrees, more towards 22.5) and fires a LOT of bullets. Like seriously, this thing basically creates a cone of death. Might want to dial this thing down for a multiplayer non-co-op game, y'know? Simple solution might be to leave falling and impact damage on and let people slam themselves into walls with it.
Video because it's hard to explain:
https://www.youtube.com/watch?v=N6HyI1_uyTgKatana: It's a sword. In the game, swinging it puts it a ways in front of you and has a swooshy thingy. Basically just check if there's anything in the next eight studs forward and kill it. (Not where the player's looking, forwards. Not taking vertical stuff into direction.)
Grenade Launcher: Fires 10% faster than the bazooka and the grenades bounce. If they hit something killable, they explode immediately.
Laser Rifle: Oh, this one's great. It's a melee and long-ranged weapon in one. It charges up, with a small bit of energy in front, and then fires a beam of energy. Anything that touches that beam, whether while it's charging or firing, is dead. (Most weapons are one-hit-kills in this game, since it's players vs loads of computer enemies. I think it's co-op but I'm not sure.)
If you want to know more, it's free on Steam.
I might be able to attempt some modelling.