Pretty hard for me to pick a favorite anime...
But in terms of pure guilty pleasure (and no, it's not ecchi/harem in any way), I have to pick Ao no Kanata no Four Rhythm - an anime adaptation of a Visual Novel with the same name.
The reason why I pick this apart from the other ones, such as the likes of Boku no Hero Academia or Highschool DxD (two of my favorites too, btw), is the fact that this anime adaptation of AoKana is under appreciated in terms of MAL ratings, due to the anime adaptation being so far from the Visual Novel's portrayal (which is kinda expected, considering the Visual Novel is deemed godly and with high praise due to its drama elements).
As for the anime adaptation, the portrayed plot was definitely simple, a lot of cute stuff and slight drama happening here and there, pretty generic stuff, but what still overwhelmed me is the concept of using human flight with shoes as a major element of the sport, which is not a common sight in sports anime.
Of course, no one would have guessed >.< Though big anime like that that drag on and on and on, never understood how they were liked so much/ Too much fluff and filler.
Mine is probably still Neon Genesis Evangelion, still waiting an eternity for the last rebuild >.< Sword Art Online might top it if they ever redid the anime to follow the Progressive series he started instead of skipping 10-20 floors an episode >.<