Blazing Saddles...Madeline Kahn as Lili Von Shtupp:
"Oh, it's twue. It's twue. It's twue, it's twue!
Boogie Nights(duh):
Amber Waves: Let me just check on something.
[takes off Dirk's pants]
Amber Waves: That is a giant cock.
From the film Porky's (1982):
Tommy Turner: And this is the pride of Angel Beach. Anthony Tuperello, affectionately known as Meat.
Cherry Forever: Oh, my God. The boy's deformed!
Not a film, but an episode of "Sex in the City" titled "Ex in the city.
In this episode Samantha faces a challenge: she meets a man with a huge penis. So big that she isn't sure she can take it. When the doubt becomes a certainty, she proposes they just remain friends for the safety of her own vagina!