Laser is the perfect weapon for trickjumps and moving around the level. A very unique thing.
The shotgun is the starting weapon but it really packs some power and can be strong weapon and is useful as a finisher.
If i remember correctly the machine gun is the strongest gun when calculating damage but its hard to hit each shot and it takes some time to deal the damage.
The mortar is a very good all round weapon. It deals quite some damage, the arch from the projectile makes it hard to dodge, it can be used to lay traps and it has a high push.
The electro.. you should compare that gun to the rocketlauncher from other games. It has a fast projectile, does high splash damage but is slow. So you have to USE it like the rocketlauncher in quake3. Pre-aim you opponent and fire at his feet to get splash damage. The secondary firemode is useful to lay a field and then set it off with the primary mode which will cause extra damage kinda like the ut shockrifle

The crylink is really hard to use but it deals quite some damage. Only few players like it as its hard to aim with it.
The nexgun.. oh snipers love it.. whats more to say about it.
The hagar is a mix of the machinegun and the mortar. A bit harder to aim but the bouncing on the secondary firemode is quite useful to trap someone.
The rocketlauncher. Quite different from other games as its really slow but super powerful and it can be set off with the other attack button.
My favorite though is the mortar.. its THE alround weapon, its impressive if you hit someone in the air and just fun to use.
*edit* wrote mortar instead of hagar, thanks for noticing