I am weird and generally rewatch more than I watch new. I've been breaking myself of that a little the last few months, making myself watch new stuff. But I am also rewatching My Hero Academia at the same time.
I think the shows I've rewatched the most are probibly Digimon Tamers, Yakitate!! Japan, Space Dandy, Ouran High School Host Club, Gravitation (Ugh, younger me... Gravitation isn't very good... good music though.) and the original Fullmetal Alchemist.
I feel like I've rewatched Hikaru No Go quite a few times (And 4 times for sure, off the top of my head) But it's a little longer, so it might just feel like I've watched it a bunch.