inspiring

• guy builds a kit plane — LOTS of work, but it's amazing what you can accomplish with dedication (even when there are major safety issues that need to be cared for)

welding

• redneck rollercoaster (somebody even modded it into a game)
• tracks + rollcage = win
  • Ripsaw is far faster and more mobile [1] [2] [3]
• 8-legged spider
• gixxerkart, YZF R1 kart — the power-to-contact-patch ratio is rediculous in the extreme, but pointless things can still be fun :)
• water-powered jetpack
• monowheel — far-out, but the design is starting to gain traction?

work vs play

• seat and harness on a robot arm, part2, part3 (and a far more dangerous version — take care of your wrists!)
• tank doughnuts
• loading a skid loader without ramps (I'm pretty sure this requires a second guy in the truck to back up after the bucket is planted on the ground)
  • bobcats are famously adroit [1] [2] [3]
  • a full-size articulated Catepillar doing the same thing as the bobcat!
  • excavator unloading, nice ending too :)
  • excavator mounting a traincar
  • excavator observed trials (you REALLY don't want to dab here)

unlimited funding

• massive trebuchet

software

• procedurally generated city (writeup)