I like some of them as they can be a fun time waster especially when they watch classic music videos.
BrosReact0151 - Two UK brothers, though their "schtick" kind of gets old after a while. I'm not subscribed but I do check their channel once or twice a week. Example:
India Reacts - A lovely person with honest reactions.
The Matthews Fam - Thoughtful, his reactions are funny to me at times.
Charmx - Millennial cellar dweller. He's most entertaining reacting to scary videos
Modern Renaissance Man - Smart and funny reactions
If you have recommendations, please post 'em here