Somebody already mentioned the Winnie's Homerun Derby. I also have fond memories of playing:

* N - https://archive.org/details/nv-12

* Ball Revamped - https://archive.org/details/1100_ballrevampedv2

* Mind Fcuk - https://archive.org/details/tf_20210127

* World's hardest game - https://archive.org/details/the-worlds-hardest-game_202310

* Canabalt - https://archive.org/details/canabalt_202012

* (If you're from one of the commonwealth countries) Stick Cricket - https://archive.org/details/stickcricket_flash

There's honestly a ton more, you can download the archive and go through the various community lists in there. I've spent a few evenings just having a few drinks and playing some old games! :D