Gel'ziabar Stone
This stone does not damage anyone, just pushes the enemy away, so it may be useful as a weapon only near a precipice. But it has two more functions: it glows in the areas with Scrye events and increases the power of current spell when active.
 

Revolver
A standard six-shooter. Theoretically it can kill any enemy (except bosses), though for some of them you'll need plenty of ammo. Works best against humanoids (trsanti, monks) and howlers.
 

Tibetan War Cannon
A cannon that fires ice, rather powerful. Works fine against all enemies at first levels.
 

Molotov cocktail
Sets things on fire, but does not cause really much damage. Besides, you can carry not more than 5 bottles.
 

Shotgun
You need to reload it every second shot or, if switched to double-barreled mode, every shot. You will admit that it's not very convenient.
 

Scythe of Celts
Beheads humanoids with one stroke. This is the weapon you defeat the siblings with. Unfortunately it reduces your mana when activated. In alternate mode it temporarily increases your health at the expense of the enemy you've defeated.
 

Speargun
I like this one for its "sniper view" mode. Kills humanoids at one shot, on condition that you hit head, neck or chest. The spears can be charged with lightning, but it costs too much mana (~100).
 

Phoenix
When you throw the phoenix egg, your mind follows it and you lose control over your body for a moment. Everything happens rather quickly and ends with an explosion.