Welcome to the Hippie House of Hacked Tools!
When I need a special tool, I reach for my box of <$1 yard-sale tools--or the boneyard.
I needed a chuck for my impact driver:
Chineseium chuck and spindle from a trashed DP out of the boneyard, rounded-out 5/16" nutdriver bit. I only needed this for one job, so just slapped it together with some MIG goober-welds. Since then it's actually proven to be very handy--like a left-hand bit for removing a rusted, busted stud with some impact, so I think I'll grind that down and try to do a better weld with the TIG.
Some specialized wrenches for working on old (pre-WWII) Coleman lanterns:
I wanted to replace the donut spare of my Toyota CrownVictrolla with a full-size one and get it out of the trunk. I needed to fabricate a spare tire holder to fit my (hacked) roof-rack, so:
A 5/8" stud (all-thread), a nut to fit, welded into a 3/4 box-end, cut off for convenience, some paint and heat-shrink tubing. The collet that fits the wheel opening is a 2" cap for Tri-Clover brewery fittings, with a 3/4" hole drilled in it and a 3/4" nut tack-welded on.
It works:
Hell, the roof-rack itself is a hacked "tool": A shelf unit for warehouse racks with some railing from a kitchen Euro Rack welded to the sides.
Those are just the ones that are close to hand. I have dozens more around here.