Everyone going the biggest and best....

I suggest:

Both versions of House on Haunted Hill (evolution of the campy horror genre)

Both versions of Black Christmas (see horror tropes become them and the retelling)

Jason X (Jason the undying killer but in space!)

Teeth (if you needed a movie to really drive home that SA is bad)

Trainspotting (if you needed a movie to really drive home that drug addiction is bad)

The Room (a detailed instructional of how not to write a movie)

Super Mario Bros 1993 (watch as both the main characters appear to become more drunk as the story goes on because their actors actually were) .... And the new one I guess. It's ok but not as entertaining on a meta level

DOA Dead or Alive (possibly the most true to source video game movie and a fun martial arts movie)

Patch Adams (if you can watch the whole thing twice, you're better than me. That third act is brutal emotionally for me)

Slaxx (do not read anything about it. Go in blind. Enjoy the layers of what the actual fuck is going on)

Dungeons and Dragons 2000 (about as accurate a oneshot as I've ever seen. Also, Jeremy Irons being peak Jeremy Irons)

What the bleep do we know (Science! Physics! Learning!)

Wicker man (Cage version during the height of him taking literally any role to pay off debts. Watch him overact and punch a woman in a bear suit)

Romeo and Juliet (decaprio version. Shakespeare but in modern day Miami. They do not update the language to current English.)

I've got more but that should be good for a few days worth of watching.