Horse's head
I've seen a whole lot of absurdity on the screen in my times but the part when the grizzly detaches the whole head of a horse with just one single whip of its claw is one of the silliest movie moments I've seen in a long, long time. It only lasted a second or two but even a few days later I'm still mesmerized by the sheer stupidity of that scene.
It's so hard to believe the mid 1970's audience took this film dead seriously and without even a giggle (though I wouldn't know, since I wasn't around then but I think it's a pretty safe as a wild guess). Perhaps someone could shed some light on this? Nowadays you would probably see something that ridiculous only in a really exaggerated, screwball horror comedy.