I_Am_Mod's custom camera mount made me think about it, and having a thread where we share the stuff we've made in the past could also be great to give people ideas, as well as just share our work.
To get it rolling, here's the updraft firepit I made out of rolled 11 gauge 304 stainless plate about 5 years ago. Note the holes around the base and in the raised floor of the pit- they're designed to suck air in and up through the coals rather than down from above and DOES IT EVER WORK! This thing is an incinerator. It's like having someone blowing on the coals the whole time. You can pile logs up as high as they'll go and not snuff the fire. It's uncanny how hot it burns and how little ash is left at the end because of all the airflow. I plasma cut all the artistic details out by hand (which look really cool when it's got a fire going in it) and punched all the holes for the updraft using an ironworker. She's about ready for another paintjob, but otherwise unfazed by half a decade of rippin' fires and drunken debauchery.
So what have you made?