I have done several.
A helix (it will be hidden but still is functional)
Wiring (it was hidden but functional mess)
Stubb switch (again, functional, I can build them much better now)
A mountain out of paper mache (my first). It looked like a pile of elephant dung
There are probably several others.
My how I envy neatness freaks. I won’t name them but you know who they are. One fellow’s dummy cardboard buildings look better than some you can buy.
Dave Vergun
I tried building a water tower out of a coffee can. It was so ugly that people laughed at it so I took it apart and now it hold train parts on my work bench. It works much better for that than as a water tower. I will try again but this time I will make it all out of metal and solder the legs up from small tubing. the first one was made from a coffee can and wood strips. Bad. Really bad.
That’s multiple for me. Mostly I don’t have the patience to model something which takes more then an hour or so… Result is a swftly build “thing”, counting to that: also a heap of elephant dung out of paper mache, a metal bridge, soldered together from lengths of old h0 rails (it was so uneven that trains couldn’t take the grade of the wobbling), a sort of motorized passenger car I saw on a picture, which still has to be finished etc.
Most of the things which have an ugly outcome are things which I build with haste…
My marrage didn’t start out ugly, but it sure got that way when I divorced her.
Paul Goodness
I modeled a bunch of Norfolk Southern bosses in a Conrail yard after the split. There were a bunch of them hiding in the bushes waiting to take an unsuspecting brakeman out of service.
Sorry - below the belt but I couldn’t resist.