Prime Clone
Super Freak
Plus, it's the movie that introduced midichlorians (for seemingly no reason, since nothing on screen before or after gains any deeper value for it).
They bugged me for a long while but I got used to them (especially with their relationship to real-world science). Plus the mention in ROTS helped validate them.
Let's face it guys, the OT is the key to everything. It's why some like the PT, some like the ST, some like both. Without the OT we probably wouldn't like any of it.