Cujo's up there... I've got one that will beat it though.
When I was in college, a buddy and I went to the local video store. There was a movie called something along the lines of 'Caveman', not the one with Ringo Starr in it. Back said it was something to do with a caveman following the people that killed his tribe. I don't know why we picked it up, but we did.
So... Caveman returns from a hunting trip, finds all of the people at his collection of huts dead, stuff on fire. There are tracks leading away from it. For the next hour, you are treated to video of the caveman walking through wilderness, looking at the occasional animal that he passes by. Caveman eventually comes across a nest of ostrich eggs, uses a bone to break them open. Realizes the bone can be used as a club. Walks again for another 20 minutes or so. Winds up at a cliff. Throws the bone off the cliff. The end.
After the first 10 minutes, it became an exercise in morbid fascination for us to see what happens next. We were left in awe that this thing existed.
If you're going to pick on Starship Troopers, the third one is by far the worst of the lot.
Wiley.