Here's another part I thought was funny:
Napoleon Dynamite: [referring to Deb's milk] I see you're drinking 1%. Is that 'cause you think you're fat? 'Cause you're not. You could be drinking whole if you wanted to.
Trisha: I wanted to thank you for the beautiful drawing you did of me. [Through gritted teeth]
Trisha: It's hanging in my *bedroom*.
Napoleon Dynamite: Really? It took me like three hours to finish the shading on your upper lip. It's probably the best drawing I've ever done.
Kid on Bus: What are you gonna do today, Napoleon?
Napoleon Dynamite: Whatever I feel like I wanna do. Gosh!
Don: Hey, Napoleon. What did you do last summer again?
Napoleon Dynamite: I told you! I spent it with my uncle in Alaska hunting wolverines!
Don: Did you shoot any?
Napoleon Dynamite: Yes, like 50 of 'em! They kept trying to attack my cousins, what the heck would you do in a situation like that?
Don: What kind of gun did you use?
Napoleon Dynamite: A freakin' 12-gauge, what do you think?
Who else thinks this movie is funny?