Always loved knives as a kid. I'm not sure I'll ever fully understand why... Maybe it was the "you can't have one until your older" appeal, or watching movies like Rambo and Crocodile Dundee. I can remember cold hammering a 16 penny nail flat on the concrete floor on my Grandfather's garage to "forge" a sword for one of my G.I. Joe action figures. I even sharpened it.

I couldn't have been more than 9 or 10 at the time.
A few years later, I was in my dad's shop trying to find some flat stock to make a knife out of. The only steel I could find was a piece of 1/8" wall square tube, so I used an angle grinder to try and cut one of the sides off, until it curled up like a pretzel. I burned through an entire grinding wheel (NOT a cut-off wheel, haha) and didn't get anything for my trouble. I think I was more worried that my dad would find his grinding disk all used up, and forgot all about making knives for a while.
Fast forward a few years later, after I'd graduated college and gotten married, I happened upon a thread on Bladeforums.com about something called a NWGS, and then I started reading about how guys were making knives out of their garages, and even in some cases their apartments, and I couldn't believe it. I thought you had to be either a) an old timey blacksmith, or b) a million dollar machine shop to turn out a "real" knife. I started reading around Shoptalk and found guys making works of art with little more than a few homemade tools, files and sandpaper. From that point on, I knew I wouldn't be satisfied until I made one. Used a Shopsmith and a couple low quality tools to make a NWGS, then a heat treat oven, and then I grabbed the bare minimum for making a couple of kydex sheaths and got to work on some VERY crude neck knives. Been hooked ever since! Oh, and I even found a few posts and videos by some guy named "JT". Helped me learn a thing or two as well.
Now, the ability to just think of something I want to make, and then turn it into reality is the main driving factor. Something about making an idea real, just does it for me. If I can make a few bucks here and there, or buy/build another tool or two, that's icing on the cake.