Well for me a guilty pleasure film is anything that you like, but is targeted at a much younger age-group or totally different audience than yourself, or is something which is so bad it's good.
So taking that into consideration I'd have to be
Tinker Bell and the Great Fairy Rescue and
Piranha 3D.
Tinker Bell and the Great Fairy Rescue was much better than expeceted and could suprisingly be enjoyed by adults as well as 5 year old girls.
Piranha 3D is possibly the ultimate guilty pleasure film and was one of my favourite movies of 2010, so I can't wait for the sequel.