Holy shit, you want me to pick just one line from the best parody movie of all time?!

I guess if I were forced to pick, it would be:
“I am your father’s brother’s nephew’s cousin’s former roommate.”
“So what does that make us?”
“Absolutely nothing.”

I’m surrounded by assholes!

Honorable mention because I use this one surprisingly often:

1-2-3-4-5? That’s amazing. I’ve got the same combination on my luggage.

Comb the desert. “We ain’t found shit!”

No more beaming! This time, I’ll walk! opens the door and it’s right there

I agree with @ringwraithfish about that being a very hard choice.

…

Nope, can’t decide between (all paraphrased because I mainly remember the German translation)

• “Comb through the desert!” [cut, followed by troopers using a giant comb on the sand]
• The passcode scene
• “Water, water!” “Water, water!” “Oil, oil!” “Roomservice, roomservice!”
• “Didn’t I say only pack what we need for survival?” “But I can’t live without this thing!”
• “Yoghurt! I hate Yoghurt!” [followed by underling offering to change Big Helmet’s breakfast and a rebuke that that wasn’t what he meant]
• “He’s an Asshole, sir.” “I know that, I want to know his surname!” “That is his surname, sir.” [Big Helmet asks who else on the ship is an Asshole and nearly everyone holds up their hand.] “I knew I was surrounded by assholes!”