Okay, the entire movie is worth quoting, but here are a few of my favorite scenes:
French Soldier: I don't want to talk to you no more, you empty headed animal food trough wiper. I fart in your general direction. Your mother was a hamster and your father smelt of elderberries.
Sir Galahad: Is there someone else up there we can talk to?
French Soldier: No, now go away or I shall taunt you a second time.
Sir Galahad: Zoot!
Dingo: No, I am Zoot's identical twin sister, Dingo.
[He tried to get past her]
Dingo: Where are you going?
Sir Galahad: I seek the Grail! I have seen it, here in this castle!
Dingo: No, oh no! Bad, bad Zoot!
Sir Galahad: What is it?
Dingo: She has been setting a light to our beacon, which, I've just remembered, is Grail shaped. It's not the first time we've had this problem.
Sir Galahad: It's not the real Grail?
Dingo: Oh, wicked, bad, naught evil Zoot! Oh, she is a bad person, and she must pay the penalty!
Dingo: You must spank her well, and after you are done with her, you may deal with her as you like... and then... spank me.
All: And me. And me too. And me.
Dingo: Yes. Yes, you must give us all a good spanking.
Dingo: And after the spanking, the oral sex.
Galahad: Well, I could stay a bit longer...
The Knights burst into the Abbey and pull Galahad outside.
Sir Lancelot: We were in the nick of time. You were in great peril.
Sir Galahad: I don't think I was.
Sir Lancelot: Yes, you were. You were in terrible peril.
Sir Galahad: Look, let me go back in there and face the peril.
Sir Lancelot: No, it's too perilous.
Sir Galahad: Look, it's my duty as a knight to sample as much peril as I can.
Sir Lancelot: No, we've got to find the Holy Grail. Come on.
Sir Galahad: Oh, let me have just a little bit of peril?
Sir Lancelot: No. It's unhealthy.
Sir Galahad: I bet you're gay.
Sir Lancelot: Am not.