A Steampunk Stratocaster (Score 1)

That's hard to say - the most recent thing you build like the Steampunk Stratocaster I just finished always seems the coolest right then.

The heaviest thing I ever built was a Schoolbus to RV conversion

and if number of links on the intarweb count toward coolness the Retro Cellphone Handset is the coolest.

Jake von Slatt.