A Certain Scientific Railgun yearly. It’s what got me into anime back in 2021, started a >4 year long streak of watching anime every single day. It’s not a set date, I just start the rewatch 365 (366 on leap years) days after I last finished it. I’ve seen it four times now: first subs, then dubbed, then again in '23, then again in '24.

Haibane Renmei roughly every spring. Part of a discord server that did a group rewatch in '24 and '25. Looking forward to next year