I mean seriously. You had an idea, drew/painted it, etc. then some time later you look back on it and felt a "what was I smoking?" so strong that you had to actually, personally, permanently dispose of it in some manner?

In my history....

The first was the only genuine TF sequence I've drawn to date. It was back in 2004, subject being a random human subjected to a TF into a three-headed hydra. Torn clothes, body horror, the usual stuff. There is only one copy of it left on the Internet, over on my FAC page somewhere (if you're really that desperate to see what it was). I did not (and will never) upload it here, especially knowing what sorts of fetish-catering stuff that the TF genre produces. I still have my scan files of the damned thing, but the original has long since been reduced to ash and scattered to the winds.

The second was also in 2004 after various attempts at drawing Sora (of Kingdom Hearts fame) as a red lion -- this was before the knowledge that there was actually going to be a Kingdom Hearts 2, before the announcement that Lion King was going to be one of the worlds (and with Sora as a black lion). There is one copy still buried in my deviantART gallery somewhere, but likewise, it's the only copy you'll find anywhere because the physical original ... "no longer exists."

The last was in 2006, a fanart of another artist's gryphon, a normally anthropomorphic character but rendered as a feral form. The piece itself wasn't bad, probably even my best coloring and detailwork at the time, but it became the subject of a personal dispute between me and a third party and I ended up losing that dispute pretty badly. (By which I mean "genuinely considered throwing all my art supplies in the fire to watch them burn" badly). The gryphon was an innocent but casualty of war, and you won't find any copies of it anywhere, not here, not dA, not FAC. I still have my scan files of it, of course, but the original is now in the hands of the artist whom it was a fanart for in the first place (physically mailed and sent).

There are a few other pieces I've never uploaded over the years because I managed to give away (or misplace) the originals -- one was a semi-mechanized dragon (transformable between quadruped and bipedal forms) which I gave to a friend, the other was an anthropomorphic avian which I gave to my old H.S. art teacher. Neither of these I would consider disowned, but I never took any scans of them, making them my most elusive pieces ever.