Well... I have been surrounded by spudguns for a while, but only started building my own at the end of my sophomore year.
When I was in the 5th or 6th grade, I went to one of my friend's parties at his house. His dad, a retired geologist, got out the spray-n'-pray combustion at started sending Excedrine bottles across the yard.
Well, of course, I told my parents I wanted to build one, and the answer was of course, NO. Fast forward to August 2005.
Hurricane Katrina blew through and we went to Illinois. When we came back, I had nearly an entire month ahead of me with no friends or school, so...
I started off small. Hunting in the mornings for squirrels and such. By the second week or so, I was actually reloading 0.38 Special cartridges with 0.32 caliber buckshot "bullets" with a little wadding. After this, I was starting to get really bored.
So, one day, I grabbed my backpack, some random crap, and walked the few miles to my friend's house. He showed me the DPC-400.
Truly amazing in my eyes at the time, even though he couldn't get it to fire at the time. 1-1/2" chamber and 3/4" barrel with a powerline 3-9x32 scope mounted as well. He had fired it quite frequently before I got there, but it just wouldn't work for us.
So, fast forward yet again to later in that school year, he built another model with a larger 3" chamber for easier fueling. We went for a couple of Friday nights firing CO<sub>2</sub> cartridges, lightsticks, and paintballs without incident. We finally discovered our favorite ammunition: Dum-Dum lollipops. These fly amazingly straight and could actually put a hole in tin when shot with the right mixture. Of course, I was truly intrigued by then, until it blew apart one night. So, I decided to make my own, using air pressure. A pneumatic had to be safer than a combustion, right?
And the rest, they say, is history. I got some 3" SCH-40 from an arrow case a guy from the local archery shop sold us arrows in, went and bought some DWV fittings and a sprinkler valve, and I was set. For a month or so afterwards, I was shooting all the standard ammunition better than the old DPC. Of course, then I realized the components weren't pressure rated, so I scrapped the cannon and turned it into my first combustion. Everything went downhill after that and the rest some of you know.

The summer after Sophomore year was full of much boredom. Before I eventually got a job and really started the building, one of our best friends and my friend's girlfriend moved to Texas, creating a little boredom. But, I wouldn't trade it all for anything.
And of course, I wouldn't be close to where I am at now without the SGTC forums and later, Spudfiles. What can I say... *sniff*...
I love you guys...