It started with a Big-Wheel. The Christmas morning I got it, the fat kid next door took it and broke the fork off before I ever rode it. I cried to my parents who said "that's the way it goes". I passed this important lesson on to my little brother and commandeered his Big-Wheel.
When I was 14 I excavated my dad's old bike from the tool shed and started riding everywhere. It was a huge, heavy, yellow, Schwinn 10-speed beast. I was always standing up and cranking hard. My thighs stopped fitting in my jeans.
At 15 my parents gave me a Univega touring bike. It was great while it lasted but was stolen at a store where I was contemplating which model airplane would be the coolest to blow up with fire-crackers. A year later I had a drivers license and didn't care when the police recovered the Univega from a field.
When I was 22ish I bought an '88 Specialized Stumpjumper on a whim. Just as I was realizing how fun trail riding was I crashed and ripped my arm out of it's socket. By the time I had recovered I had moved to Park City where I began to explore the alpine trails.
I bought a newer ('92?) Stumpjumper with a 1.5 inch suspension fork. I went on my first trip to Moab, where biking became part of who I am. It was a revelation. The landscapes, challenge, and exhilaration were a combined experience I will never stop pursuing. A year later I moved to Salt Lake, parked my car, and spent a six months riding for my primary transportation and recreation.
My Cannondale Super V 1000 was stable, light, responsive, and strong. Coming from a cross-country riding background it seemed very plush with 3" full suspension. It got stolen from the back of my truck after a few years or good riding.
The Cannondale 2000 Jekyll was my least favorite bike. I was too big and riding too hard to keep being a weight-weenie. It was 28 pounds with about 4 inches of travel. Once I fitted it with higher rise stem and got out of the face-first cross-country position, it was much easier to ride bigger obstacles. I broke 3 wheels, the frame, and the swing arm while I owned it. I sold it.
My Cannondale Gemini 900 was a used rental. It had 6" travel and weighed 35 pounds. I never worried about breaking it and I could still pedal up anything I wanted. The suspension design was primitive so it tended to buck on jumps and was hard to balance, but I had a great time on it. I rode it for 3 seasons before it was stolen from the back of my truck.
I bought a BMX bike with a banana seat at a garage sale and kept it at my office. It was similar to my Scrambler, and a pretty comical ride for a 6'4" adult. I'd ride it around campus to meetings and classes, and even rolled downtown for lunch. (I work at University of Utah which is uphill from downtown Salt Lake. I never locked it and it was never stolen. Hopping the train back to my office was mandatory because "Scooty Puff Jr" was too small to actually pedal. I gave it to a friend who wanted a Burning-Man bike.
My little BMX cruiser was so much fun I decided to get a real cruiser I could ride to work. I ended up with an Electra Townie 24. With a few upgrades I had a fun, relaxed bike, faster than most mountain bikes on my commute. I keep it on hand now as a 'breakfast bike' to roll down the cafe late weekend mornings.
My current trail bike is Trek Session 77, another used rental. The suspension design is more advanced that my previous swing-arm bikes, and the difference is huge. For the first time I can do transition jumps and balance obstacles are much easier. It has 7" travel and weighs over 41 pounds. I can still do all the major climbs around Park City, but it is work.
Having a third bike certifies one as a bike nut. I bought a hardtail (another rental) in Park City for $250 and commuted it for about two weeks before it disappeared from a coffee shop. I missed it. A friend pointed out the Nashbar Signature frame, an inexpensive, high-end material/construction hardtail. I put a ridged fork on it and discovered ridged hurts, even on the street, so I'm running some bigger slicks that can soak up about an inch of impact. My fave feature is the 1x8 drive train with an old-school lever shifter. For the intended task this bike is simple, fast, fun, light, strong, and I love it.