I remember some movie, I think it was from the 50s or 60s (maybe the 40s).
The main character had found a lot of money or something, but not that much. So he goes and runs into a casino with a girl and places a large bet on a roulette wheel. He thinks it's his lucky day, but the roulette guy knows him and says he won't let him make the bet. The casino owner tells the guy to let him make it, and then the main character loses.
I remember that it wasn't Rain Man, but that's all I remember.