Damn this game is filled with hilarious weapons, like every second one is an in your face reference.
I found quite a few interesting ones in my first playthrough, but far from all!

Here are some of the coolest of the ones I found on first playthrough:
Stung - sword from LoTR, in goblin caves, glows when enemies are near
M60 - FUCK YEAH, COME GET SOME, totally ridiculous yet fun weapon which is hard not to get
Arcane Saber - yep you guessed it, it's a godamn lightsaber does a lot of dmg per hit and swings really really fast too, found in lava filled dungeon
Exotic Bade - not much in of itself but it is dropped by npc Highlander after the airship sequence, made me laught killing the dude
(there are some others but they were not quite as entertaining)
 
Kewl stuff I found out exists after finishing the game:
Knife of Counter Striking - obvious reference is obvious, gives perma haste, OMFG i want this thing
Mjolner - hammer, makes lightning strike, figure it out ... :)
 
(oh and Excalibur Brad found in QL was priceless, especially the way you take it out)
 
SO WHAT ARE YOUR FAOURITES?

The Sword of Mastery is great. Its a Zelda Master Sword ripoff. Even the area you find it in plays out just like A Link to the Past, with rabbits and squirrels running around. Its actually a great weapon too, it does 400 damage a hit if you're hurt and 800 damage and shoots arcane blasts when you're full. 

The Sword in the stone gave me the biggest laugh. You find it in the corn field owned by the quest giver (you know who I talk about).
 
The M60 and Saber, while fun and awesome to use, are a bit too silly for the humor built overall in the game.

Knife of Counter Striking sounds fantastic.