Was Definitely Jody Foster, from a very young age, as we were only about a year or two in age different, and I had a thing for tomboys from a wee boy, and I saw ALL the pictures she was in. I just thought she was so cute and cool.
My very first girlfriend taught me how to "jump" my bike over anything, she wanted to be like Evel Knievel, and you did NOT want to get on her bad side! She's the one who taught me how to take mean boys down by kicking them in the b@11z.
The earliest one I can think of was Rachel Leigh Cook from that anti-drug commercial. Her hottness was quite possibly the reason that I decided not to become a heroin addict when I grew up...