The first that comes to mind for me is The Breakfast Club and I hope it never does have a sequel or remake
The Princess Bride is another good one
Edit: another one of my favourites is Wall.E, my favourite Pixar movie. There are also several other Pixar movies that don’t have sequels or remakes yet
Check out Tapawingo, it’s not a sequel but it stars Jon Heder and has the same kinda mood: https://www.imdb.com/title/tt14146836/