Probably
Scream, because it works well enough if taken seriously but is also a parody of the genre at the same time. In a similar vein, I do like the first two Scary Movies but haven't seen the subsequent ones and the other parody films in that franchise seem pretty lousy from what I've seen.
Not Another Teen Movie is a guilty pleasure as well.
Chicken Park also deserves a mention. To be honest, it's a downright awful movie, but it's such an obvious and ridiculous parody of
Jurassic Park that doesn't even try to take itself seriously that it's entertaining.