I have too many.

1) My neighbor threw away an ITT cobra head fixture that had been used as a yard light. Of course I was about 10 at the time so I couldn't get it.
2) The house next door had some cool fixtures. There was a chrome fluorescent light over the sink in one bathroom with a turn switch on one end and an outlet on the other. I was there as they were putting it into the trash and they said I was welcome to it, but again I was about 10 and mom said no. The other bathroom had a porcelain Porcelier sconce. I asked to have that one and they were going to save it but it got broken. But I do still have the pull chain socket. There were also porcelain pull chain sockets in all the closets but I wasn't able to save them either
3) The house on the other side had a round post top light from the 1950s I guess. It got thrown away when the house was demolished. There were also some other wall outlets I wanted to save from it but I wasn't able to get them.
4) I also like ceiling fans and I've missed out on MANY thrown out on my street. Emerson 1895 series, Fasco Great Room, Emerson Heat Fan, CEC Georgian and others.
5) On another house a neighbor was remodeling recently, they've put a few cool light fixtures and fans at the street in case anyone wanted and I missed out on them too.
6) I seem to recall seeing at Habitat a year or two ago, I'm pretty sure there were a bunch of those MH louver fixtures 2x2. They were too big for me to get though, I don't know if they somehow ended up there when the old Publix being demolished or not, but could have been.

If only I was older when this stuff got thrown out! Nowadays I don't see anything of these sorts. The Fasco Great Room was really my fault. I saw it sitting in a box when I was going for walk, and went back home thinking I'd get it later when it was dark out because I felt embarrassed to take it. But when I went back to get it, someone else beat me to it.

The only one i can think of i wish i grabbed was 30 or so GTE Sylvania F40T12's from a junkyard that were all lightly used.

Also, a few weeks ago I saw a white plastic Regent MV bucket light in the box in pictures for a yard sale. I wasn't able to go the first day of the sale, but when I went the next day to see if it was there, it was gone already.

Went inside an abandoned house that was two stories high and is falling apart. Anyway there was two wall mounted F40s but the day I went, that room was about to collapse. The next time I returned (which was two days after the first day) the same room was collapsed and both fixture were bent in ways that make it unrepairable. The tubes were gone but I don't think they were anything special. I haven't returerned since then because I'm afraid the second I walk in, the whole thing will fall on me.
Fixtures aren't worth my life or some damage to me.

-15 years ago I found nice incandescent/sbmv streetlight with mounting arm included. It was on back storage of a second hand shop laying in a pile of stuff. The owner was not sure how much to ask abot it so we agreed I come back later when he had think about it but then it kind of forgot.

-mv obstruction lights that were left at the cellsite after being replaced with led at some point. I was so hurry to get the next job site I had no time to find one that had all pieces. I kinda forgot it and when I went there next time someone had cleaned the place and threw those away.

-didn't buy mv spanwire lantern while they still made such things.

I've always wanted an airport beacon. I am speaking of the kind you see with the green and clear lenses that rotate and denote an airfield at night. I had the opportunity to buy one about 10 years ago for about 75$. The unit was in excellent condition, was fully functional, and setup to run off of 120V. This was an absolute steal, and I forwent the opportunity. These things are very rare to the likes of eBay and other auction sites, and frequently sell for >500$. I still do not own one.

I saw a 4' T12 louvered fluorescent fixture with at Restore once that I passed up on thinking I had no room/use for it. I still haven't come across one at Restore again. I think I might even have a picture of it somewhere. Another thing I remember was a 1980s Sylvania 400w clear tubular mercury vapour lamp. It was $20 and I found it too expensive as a Restore item for my liking.

Finally, I wasn't around to see it but I would have liked to score the 1982 Westinghouse 100w HPS OV-15 that was in front of my house. It was replaced with LED in Spring 2014.

There was also some stuff at Restore that I only bought one or two of the numerous that was there that I later wished I got more and is no longer available.

-F40T10 powertwists, I think I bought 6 out of the two cases available.
-F30T12/CG, I did buy 4 of them so I don't really regret not getting more at the moment.
-Sylvania 100w /DX mogul based mercury lamps, I bought one out of the 6 that was there. I sometimes wish I bought at least one more.