Ahh. Ghetto Gear, my bread and butter.

I have a pile of welded up fixed gear wheels/hubs, most with bent axles.

Homemade chainwhip = crobar + old bmx chain.
Bench grinder + 9/16" wrench = Schwinn pedal wrench (make it slimmer).
Old can of spraypaint + grips = easy install + adhesive that will last forever.
Old Schwinn seatpost too short? Stick the seat (male) end of one into the bottom end (female) of another, weld it together, hit it with the grinder and whalla extended seatpost that is pretty damn strong.
My old headlight was stolen, but the theif forgot my battery (really nice water bottle one), wired it up to a $10 bell headlight and it lasts forver on one charge.