Mountain bike. I didn't want to pay $1500 for the light racing bike I wanted 10 years ago. I found an unbelievable deal on eBay for a bare frame ($85) and assembled the rest myself. A childhood of wrenching on my own bikes was an advantage of course. I think the total cost was $500 and most of that was the suspension fork. Its still going strong after replacing the chain and tires every couple years.