I help out friends with their bikes. I do small tune-ups for them and install the odd component or two as well. I've also helped quite a few with used bikes and getting them to running order.
In the past year, I've gotten to work on a Specialized Tarmac S-Works with SRAM Red and Zipp 404's that weighed in at 13.5lbs. I've worked on some badass tri-bikes too.
During the past week, I've been helping a buddy upgrade and tune his Cervelo for the upcoming tri-season. Its been fun.
When I started, the bike weighed in at just a smidge under 20lbs! Since then, I've added a KCNC cassette, KCNC brakes and a set of used Neuvation carbon aero tubular wheels shod with Zipp Tangente tires.
All up weight is now 17.96lbs and it definitely feels better.
The other interesting detail I found was that while my buddy is significantly faster than me, his bars are much higher than mine when on the tops. We're in the process now of looking to see how low we can get him and still keep his efficiency high. Low is useless if you can't breathe and pedal!