Ok, I'm cheating, as this probably wasn't even really a "hit" by mainstream standards,
but God - My Pal.

These kids were too young to even get into the pubs they played, but 20 years later this song still kicks arse. God bless God.

Her Head's Revolving - The Three O'Clock

See also: Jet Fighter - The Three O'Clock

I always have trouble with the one-hit wonder designation. Both because of the point, made by others before me, that even getting one hit pretty much puts you in the upper 99.9% of people who have ever played pop music, and because, with rare exceptions, the record companies almost always have a follow-up single. And, often, the one-hit wonder is also an underground hero or a longtime iconoclast or something--two good examples are Chumbawamba and the Grateful Dead.

That said, here's a song that I'd forgotten about for years:

White Trash - Apple Pie

Some actual one-hit wonders (using US Top 40 charts as my criteria) I just can't call one-hit wonders because they have too many songs that are personal faves (Thin Lizzy, T-Rex, Easybeats, Nick Lowe, Bo Diddley, the Standells, Randy Newman, and a host of garage and surf legends from the sixties). But here are a few faves from artists that I really never found much in past their big hit:

ACE - How Long

ERNIE K-DOE - Mother in Law

the EXCITERS - Tell Him

But my favorite one-hit wonder would have to be a song I could not hear enough of growing up:

DAVID ESSEX - Rock On

The Rainmakers "Small Circles"

I doubt I could even name a top 40 single from the last 25 years besides Creep. For 70s one-hit wonders, a good source is the Have A Nice Day collection. I downloaded all 25 CDs and found a few dozen great one-off pop songs that I had forgotten.

The best such collection though is Nuggets.

Rock On was used as the theme/jingle for Q102 in Buffalo when I was growing up. Or maybe some other station. But I remember the song.

WAIT!!!!

How Long wasn't Hall & Oats????

I doubt I could even name a top 40 single from the last 25 years besides Creep.

and maybe 'Hey Ya' and a few others, and that's a damned shame, since I can appreciate the art of great hit single as much as anyone. This speaks to something, I'm not sure what.

I'd say maybe the last 20 years, just to qualify, but the death of the hit single....kind of sad.

Best ever.
Honourable mention.

Here's a one-hit wonder from not-quite twenty years ago that I believe you're a fan of, jonmc.

(Speaking of one-hit wonders: those dudes recorded at least three albums. And like a lot of ohw's, this song is pretty divergent from the rest of their output. Like Ozomatli's 'Cut Chemist Suite' (maybe because I've got the 12-inch), though that wasn't much of a hit.)

I love Tainted Love by Soft Cell, but the original by Gloria Jones is way better.