In this satirical movie of the "not another" genre, Mia Kirshner and Beverly Polcyn, a woman about thrice the age of every other actor in the film, recreate the famous Sarah Michelle Gellar-Selma Blair kissing scene from Cruel Intentions. With Polcyn very obviously being more than a few decades older than Kirshner, the stage is set immediately for an incredibly gross kiss.
The aggressive, wet, and sticky (there's a glob of gum involved) tongue thrusting that follows brings the scene to a new level. It's undeniably disgusting, yet for us, maybe a bit too obvious to make it to the very top of our list. Next time, Polcyn.