The very definition of "not for everyone", Tusk is an oddball, absurd, twisted midnight movie that plays more like a demented fever dream than a horror or comedy film. I'd never recommend it to anyone I intend to ever speak to again.
Here are the reasons why you won't like it:
1) It's unexpectedly surreal, with little interest in the laws of reality, or at least modern medicine and police work. And it's not directed in an obviously surreal, arty fashion like, say, a David Lynch picture, which makes it even harder to wrap your head around.
2) It's got an odd tone. There's comedy, sure, but it's mostly a slower, more cringe- inducing variety than Kevin Smith is typically known for. There's suspense, and a bit of gross-out, but the film evokes more unease than outright scares, and the grotesqueries are more evocative of a nightmare after eating one too many sliders than, say, Saw. And it swings freely between the two with no warning at all.
3) You haven't seen Tod Browning's "Freaks", a classic bit of cult cinema that Smith has made references to in other films. In fact, you probably don't even know it exists. (Cinephiles will notice rather direct references to many of Kev-O's other favorite movies as well, including Silence of the Lambs and Jaws.)
4) You're Canadian, and your country and culture are No Laughing Matter.
If for some reason none of the above applies to you, may I recommend "Tusk"? It's oddball, gonzo, at times self indulgent and slow, but also occasionally very funny and strangely thought-provoking, provided you're willing to go along for the ride. It'll make an impression...especially if your short-term memory "isn't what it used to be."