My guilty pleasures? Oh, so many!!! Here goes...
Barb Wire - hilarious sci-fi spoof of Casablanca.
Masters of the Universe - hokey rubbish made much better courtesy of Frank Langella's Skeletor and Meg Foster's Evil-Lyn.
Supernova - I am one of the handful of people who like this movie; can't really explain why.
Battlefield Earth - I am one of the two people who like this movie (the other is the director!). Apart from the headache-inducing camera angles, it's good pulp sci-fi trash, and Travolta/Whitaker make a great double-act.
Striptease - possible the only Demi Moore film I like. This film is hilarious. Best of all is the villain, who has the "why the heck did I ever sign up for this film - my agent is fired" look all the way through.
Mortal Kombat - killer soundtrack, and tongue firmly placed in cheek. Flawless Victory!
Sheena - The A-Team meets Tanya Roberts.
Poison Ivy 3: The New Seduction - the Poison Ivy trilogy, which began quite arty and was reasonably well scripted, soon descended into gratuitous farce, and part 3 is the (unintentionally) funniest of the lot.
Girls Just Want To Have Fun - I grew up with this film; my sister watched it regularly and I sometimes had no choice but to watch too. Now I've become "institutionalised" into liking it, and I bought the Anchor Bay DVD. A bad film, but strangely compelling. Worth watching for the young Helen Hunt and Sarah Jessica Parker.
Dirty Dancing - goes well with GJWTHF. A naff chick-flick, but if you just ignore the lousy dialogue and instead listen to the great soundtrack, it's the perfect film for doing the ironing.
Dude - Where's My Car? Surprisingly funny modern-day teen comedy. Switch brains to off-position and enjoy.
The Slipper and the Rose - another chick-flick, a musical, Cinderella, but utterly charming too. Great songs by the Sherman brothers, and a grade-A cast of supporting actors (inc. the incomparable Michael Hordern and Edith Evans).
Embrace of the Vampire - Old Mathematical inequality: Alyssa Milano naked > feeble plot + bad script + worse acting
Showgirls - for those of us who watched the early seasons of Saved By The Bell, essential viewing. Hilariously awful in every regard.
P.S. Lynch's Dune cannot be classified as a Guilty Pleasure. It is a love it / hate it movie, and its fanbase is growing (esp. after the recent, awful miniseries). Personally, I love the '84 film to pieces.
Also, Bring It On surely can't be a Guilty Pleasure. It's a good film dressed up as a bad one. I showed this to my family, and after five minutes came the comment "You only like this because of all the girls in skimpy costumes" - to which I replied "well, there is that, but it's a great movie too you know, just stay with it". By the end, everyone agreed that it was a good movie too.