Arachnaphobia didnt have a giant spider in it that guarded some witch type person in the middle of the cocoony thing (Krull). Alternatively, if you think the spider is normal size, it didnt have a person that was less than 10mm tall (on the left)
Krull was a weird film, I remember watching it when I was little, and I often thought of it afterwards, but didnt know whether I had actually dreamt the whole thing. A few times I also found myself thinking of it only for it to turn up on TV a week later!
Heres another small hint for my one. The guy facing the camera is pretty famous and has been in several cult classics. The guy facing him, whos face you cannot see, is pretty obscure (now). This film was maybe the nail in the coffin for his career, but before this, he starred alongside the other guy in 2 most excellent films. The film in question also is pretty star studded, which makes it all the better given how random it is.