I don’t have a single favorite one, so here is a top three, in no particular order:

Freefall The first webcomic i read, started in 1998 and still updating three times a week.

El Goonish Shive Another longrunner, started 2002 and still going. Helped me with figuring out some gender stuff.

How to be a werewolf Newest one on the list, starting in 2015, also still going.

Aside from what has been already mentioned, there are instances that don’t federate with Lemmygrad, whose users would not have access to the community on there, but do have access to this one here. For example feddit.de or beehaw.org.