Tremors is one of those movies that I rewatched a ton as a kid and that, in my opinion, still holds up incredibly well now. The premise is fun (alien maneating worms that sense any vibration on the earth's surface) and the mixture of horror/comedy/action is handled extremely well. I also love that all of the effects are done practically and that they still hold up until thix day 21 years later. Plus, I'm pretty sure that this is the only movie where you can see Reba McEntire as a gun enthusiast who gets a kick out of blowing up giant alien worms.
It's a really fun movie and you can check out the trailer below.