My favorites were always the names of the movies they came up with like "Cupids Rifle", "Firestorm", "Mountain High", "Chow Fun", "Agent Zero", "Brown-Eyed Girl", and "Chunnel" (The English Channel Tunnel, Chunnel, runs 32.3 miles...."). All these movies were in the Pool Guy episode, which is the one where Kramer gets a phone number that is one digit off from the Movie Phone (555-FILK).
I've always been curious what a movie like "Cupid's Rifle" would be about; the St. Valentine's Day Massacre?