Don't laugh -- I've seen extension cords twisted and spliced together with regular Scotch tape.
Me too! And not only once. I've even seen twisted wires taped with Scotch tape and buried in plaster!
Anyway, the most ingenious wiring device I've ever seen is the homebrew US 6-way Y-extension cord. I'm sure all of the US members are familiar with those flimsy dollar-store 16AWG (or maybe even 18) zip cord 3-way extensions. Several people I know too 2 such beasts, cut the cords in half, spliced the end with the plug to the 2 ends with the trailing sockets and mounted everything on a wall with some scotch tape or in the another case nailed it to the kitchen wall paneling.