Wow, a thread after my own heart. You may have already nailed it with the Christmas Story kid....he seriously makes me laugh every time I watch that scene. I need to start making a list while I'm watching these movies as I can't think of that many off the top of my head. A few I could remember though.
From Happy Gilmore:
From Annie Hall:
RJ from No Retreat, No Surrender:
Spaulding Smalls from Caddyshack: