Generic quotes
> eponymous difficulty level names
Piece of cake.
Let's rock!
Come get some!
Damn, I'm good!
> picking up stuff
Hail to the King baby!
Groovy.
> dealing with monsters
Your face, your ass, what's the difference?
I'm gonna get Medieval on your asses.
I'm gonna put a smack dab on your ass.
See you in Hell.
Hehe, what a mess.
> health related stuff
Ahh... much better.
I needed that.
> dealing with ladies
You wanna dance?
Shake it baby!
> hitting walls
Where is it?
Ugh.
> being idle
What are you waiting for, Christmas?
> mirror, mirror
Damn, I'm looking good!
Episode 1 specific quotes
Episode opening: Those alien bastards are gonna pay for shooting up my ride!
E1L1
Duke Nukem II arcade machine: Hmm, I don't have time to play with myself.
E1L1 cinema projector: Hmm. Already seen that one. (only in v0.99)
E1L2 blue key room switch: I don't think so. (only in v0.99)
E1L3 secret area: That's one Doomed Space Marine.
E1L4 opening: I should have known those alien bastards booby-trapped the sub!
E1L5 area w/ Atomic Health and dancer: Holy <something>! (I don't remember the full quote here

)
Episode 2 specific quotes
Episode opening: Nobody steals our chicks... and lives!
Episode 3 specific quotes
Episode opening: It's time to kick ass and chew bubble gum... and I'm all outta gum.
E3L? (L.A. Rumble) quake warning sign: I ain't afraid of no quake.
E3L? (Hotel Hell) Indiana Jones secret: <fake accent> We meet again, Doctor Jones!
E3L? (Freeway) Terminator secret: Terminated!
Boss fight: It's now down to you and me, you one-eyed freak!
Episode 4 specific quotes
Episode opening: Somebody's gonna pay for ruining my vacation!
E4L3 (Baked Goods): Cleanup on aisle four!
E4L? (Pigsty) opening: I'll be back (or is that uttered by some off-screen Terminator wannabe?)