And, anything Jack Black is involved with.
Almost Karmic…
Well, if KISS are a gimmick band, then Mini Kiss are a gimmick band of a gimmick band. (And, believe it or not, there was another band of short-statured folks called Tiny Kiss that were apparently in a bit of a conflict with the members of Mini Kiss.) I actually saw one of these two bands in Budapest at a music festival in the early 2000s – I think it was Mini Kiss – and they were quite good.
Well there was a band that came along in the 60’s that had the gimmick of smashing up their instruments at the end of their performance. I think a few people are still fans, so I guess I’d challenge the Village People as far as “widespread, mainstream notoriety”.
And these examples are kind of why when I read the OP, I thought, “Any good band has some sort of gimmick. Otherwise they wouldn’t stand out, and you wouldn’t remember them.” Seriously, there’s a ton of people out there who play unbelievably well. As an act in the entertainment industry, a gimmick is pretty much necessary to sell yourself as a band.
In the end, even an over-athletic playing style is a kind of gimmick. So you really just have to figure out what your (or your favorite) band’s gimmick is, not whether it has one or not. It might make you feel better about it if you think of it as a “mystique” rather than a “gimmick”. My current band doesn’t have much of one, and if I could think of a good one, I’d use it in second.
I can’t help but think we’re stretching the definition of what a gimmick is. The Rolling Stones may have been referred to as a type of anti-Beatles but they weren’t a gimmick band. But what the hell? Maybe I’m wrong. Wikipedia considers Slash’s top hat to be a gimmick.
Cybertronic Spree dresses like Transformers and plays mostly video game themes.
It always make me laugh when I see people who probably attend conservative Christian churches and vote Trump singing along with YMCA. Don’t they know what the song is about and how the Village People were stereotypes of gay men in the 1970s?
Andrew Loog Oldham made several changes to the band and controlled their images as “bad boys” in a contrast to the Beatles. If he hadn’t jumped in with that gimmick, it’s unlikely the band would have had any more than a very modest success.
OTOH, Pete Townshend smashing a guitar just happened, and only when he felt like it (they couldn’t afford new ones). It may be gimmicky, but it wasn’t planned.
Another one of those cover bands with a twist, GABBA. They do ABBA songs in the style of the Ramones.
The Blues Brothers started out as a Saturday Night Live skit and ended up having four U.S. Top 40 hits.
Mary Kay Place played country singer “Loretta Haggers” on the sitcom “Mary Hartman, Mary Hartman”, and sang a song on the show called “Baby Boy”. It was released in the U.S. as a single in 1976, credited to “Mary Kay Place as Loretta Haggers”, and reached #3 country and #60 on the Hot 100.
The Polyphonic Spree and Mannheim Steamroller are built around gimmicks.
Compressorhead is an all-robot band. You can’t get more gimmicky than that.
Chris Sievey used a papier-mâché head as a gimmick and became Frank Sidebottom.
How about The Archies. Or was there even “a band” outside the recording studio?
I very much doubt that this is correct. My opinion scoffs at your opinion.
Yes. They even made a video.
That absolutely amazing* music video aside, I suspect that the band never appeared “live.” It was a group of session musicians.
*- And, by “amazing,” I mean “amazingly cheesy.” 
This made me think of Paul Revere and the Raiders.
But I’m really old.
Warp 11 is/was an indy rock band from California, that performs original songs with lyrics entirely about Star Trek.
Say what you will.
I’m pretty sure lots of bands dressed alike.
But how many went as far as Manfred Mann’s members, who all changed their names to Manfred Mann for a while.
Or so I remember.
Nope. Just because they don’t personally espouse their often satan-oriented lyrics does not, in any way, make them a gimmick band.
Could the austere aesthetics of Kraftwerk, live, standing in front of their podium/console/computer/whatevers (with nothing else onstage except for a sort of lightshow) be considered gimmickry?
Or the mind-bending chaos of the Shaggs? Probably? Probably not?
There’s live footage somewhere of the Kinks coming onstage with the most gigantic white afros. Like, larger than gigantic beach-ball large.
Three Day Stubble used extreme wierdness as a gimmick, I suppose. Heh - or maybe thirty years later?
Daft Punk?
Slipknot?
Alice Cooper?