My Kindle has a separate folder for those - currently running at 118 entries. This is likely to grow, and may one day be published. Authors on this site who write grimdark or anything approaching grimdark - be warned!
My kindle sample folder is at 138 - but they're not all things I'll never read.
To add a few more I thought of -
The Blade of Fortriu by Juliet Mariller - It was alright, just nothing and no one super interesting in 60 pages or so
The Black Mage by Trudi Canavan - Ditto
Lord of the Silver Bow by David Gemmell - I love Gemmell! But I did have a bit of author fatigue and didn't find any of his characters that enticing for once. I also felt a bit cheated because it didn't really feel about Troy.
The City and the City by China Mieville - Great writing, great atmosphere, but nothing was happening and no one was interesting and there were a dauntingly large number of words of that to consume
Nine Princes in Amber by Roger Zelzany - Just didn't do it for me
The Monarchies of God by Paul Kearney - Not sure which one as I had them in omnibus form, but at some point around realising he was killing his most interesting character I lost interest
The Fencer trilogy by KJ Parker - The first book is a lot of fun. The second just... eh, I dunno. I forget whether I actually opened the third but I sure as hell didn't finish it.
Deryni Rising by Katherine Kurtz - Odd one this. I read one of the Chronicles of St Camber first and was intrigued although a bit put off by the heavy medieval ecclesiastical/social focus. Then I read this and it felt like a godawful prequel. Only found out later it was the original book. In any case, all a bit second rate adventure and over-noble for me
The Once and Future King by TH White - I really totally didn't get this. It would have made more sense to me written in Kazakh and I don't even know if that's an actual language.
The Dragonbone Chair by Tad Williams - Its a big fat pre-millennium epic so I should love it but for some reason it grabbed me not at all