A friend asked on Facebook what were the best Halloween costumes we'd worn. I started to reply there, but this got long, so I decided to make it a full entry.
(And I wrote this on Halloween but neglected to post it 'til now.)
The only one I remember from my childhood was a sort of generic-Renn-Faire thing, and the only reason I remember that is that my parents told me that when people asked what I was dressed as, I should tell them I was a Rennaissance Man. Only I wasn't familiar with the term, so I didn't get the joke. But I dutifully repeated it to various adults, some of whom I think thought it was amusingly clever.
Probably my two best costumes were in college:
One year I did an Invisible Man thing, with all of my exposed skin covered in Ace bandages, and bought a trenchcoat and I think a hat; I think the only thing I was wearing that anyone had seen before was my glasses. I went to a party and didn't say anything, and at first people didn't recognize me, which was very gratifying, but then someone figured it out. And there was a party game going on where people wore the names of famous people on their backs and had to guess whose name they were wearing, and someone put my own name on my back, thus spoiling the anonymity. Alas.
The other college one came about when a friendly acquaintance, call her S, walked into a room one fall day and saw me and my friend E and was astonished. It turned out that she had never seen us together before, and had always thought we were the same person; we didn't look particularly alike (I think I had a beard and he didn't, but I could be misremembering), but y'know, white college guys, similar builds, easy to get mixed up. (I sympathize; as I may've noted before, when I meet a new group of people, fairly often there are two white guys who I can't tell apart for weeks or months, but when I eventually get to know them, I realize they don't look all that similar.) E and I were so amused that we did Halloween dressed as each other; for example, I think that was the first time I ever wore jeans. We also tried to copy each other's physical mannerisms to some degree, and iIrc at one point a mutual friend turned around and saw me and did a double-take because he thought I was E for a moment.
I haven't done many Halloween costumes since college. I went to one party in Boston in drag; that was fun, though also anxiety-inducing. And there was the year that I bleached my hair for Halloween. And although this wasn't a Halloween thing, when Arthur and I did a 1940s-themed New Year's party in the late '90s, I did a fun double costume: hat and trenchcoat for a kind of detective look, and then under that a fancy-dress white-jacket-and-vest-and-bowtie suit that I'd rented from a costume shop. (I have photos, but haven't digitized them yet.) But I think that with some of these costumes, the thing that really surprised people was that I'd shaved my beard.