A Kodak Instamatic 133 - the first camera ever handed to me with a -"Here, why don¨t you try to snap some photos?"
I used it quite a lot from age 6-9 or so - by which time I'd spent enough of my allowance on 126 film and flash cubes to talk my parents into getting me some Fuji compact - I believe it was called DM10. Suddenly, I didn't have to fork out for flash cubes anymore - and 135 was soooo easy to find, compared to 126.
I still have (most of) the negatives produced by the 133; sure, they're a hit-and-miss affair (Mostly miss!) - but it is what made me pick up this hobby in the first place. Also, it still gives me a chuckle whenever someone with a 'blad shows up. -"Sure, I shot a lot of square format when i was a kid, but nowadays I much prefer 6*9..."
I can still hear the faint crackle made by the flash cubes just after they've burned out if I close my eyes and think of the Instamatic. 🙂