Mine was Star Wars: Shadows of the Empire for the Nintendo 64.
The best way I can describe this game is as being utterly nonsensical. It was part of a massive (and largely forgotten) multimedia initiative where LucasFilm wanted to tell a Star Wars story in as many different avenues as possible without making an actual film. There were trading cards, comic books, novelizations, and eventually this video game. I think the game must have assumed you were familiar with the story because it's basically lacking any connective tissue whatsoever.
It also didn't help that, as a kid, I struggled with 3D video games.
I never understood what my objectives or missions were. I never knew how to use the controls. A level would begin and I would just start walking, or driving, or flying, or whatever the engine for that particular level asked me to do. The game was a third person shooter, but you could also play it in first person. Sometimes it was a platformer. Sometimes is was a racer. I remember playing the game for hours at a time being stuck in one single level because I had no idea what to do. I would just open doors and press the action button and look for anything to interact with. I would pick up a new weapon and it would be awful and I'd have to kill myself on purpose because the new weapon replaced my default one.
I fully admit that part of my problem was not understanding how to play, but I did revisit the game when I was older and couldn't believe how flippant it was with its story and instruction. All that's really clear is that you are a Star Wars Guy and you are in a Star Wars Place. Figure out the rest yourself! Apparently the game can be completed quite easily in two hours. Maybe I just sucked.