Based on the erotic manga by Shiwasu no Okina.

Which anime would you watch over and over?

I'll just tell you which anime I HAVE watched over and over: Shimoneta A Boring World Where The Concept Of Dirty Jokes Doesn't Exist. Never have I watched a series that uses dirty jokes for comedy (with uncensored language) that's genuinely funny. The deeper meaning of the anime is in a league of its own, too.
Great series. - Re:Zero This anime is brilliant.
Nuff said. It's made by Studio Whitefox so it's not surprising how engaging the story is, the “deep” episodes, and the psychological aspects the main character is put through in another world. - Akame Ga Kill One of my best action/shounen series of all time. It breaks away from the traditional shounen junk (power of friendship, etc) and gives you something more true to life.
Without losing that shounen-touch that makes these shows so good in the first place. - Good Luck Girl Underrated comedy/parody series.
Not as good as The Disastrous Life Of Saiki K, but just as good for replay value. The main character is an arrogant, narrow minded ***** but her character development is interesting. Plus the characters are hilarious. - Shakugan No Shana This is harder to replay because it's 3 seasons long with 1 or 2 movies.
But it's mostly for nostalgia. The Shakugan No Shana universe is one of my favorites from a Supernatural/fantasy point of view.
I'd like to see another season, there's much more they can do with it. - Rokudenashi This anime still needs a second season.
That's part of the replay value.
There's still more to the story. The main protagonist is one of my personal favorites for his comedic, sarcastic personality. - Owari No Seraph Another anime that needs a 3rd season. The main characters, the action, and the overall plot is good enough to rewatch multiple times.
Though it does get a little weird towards the end with Mika and Yu. - A Certain Scientific Railgun There's nothing like the action in this anime.
And the powers of each character in particular. It's also original when it comes to the concept of espers and psychics in anime (before shows like Mob Psycho 100). Looking forward to season 3 in 2019. - Bleach It's a massive series that you can't replay too often (350+ episodes) but I've seen it enough times and it’ll always be a classic in my eyes. - Black Bullet This anime’s 2nd season is long overdue, because of the cliffhanger at the end. It’s an action series similar to Owari No Seraph and Attack On Titan, but personally I enjoy it more than both.
And have watched multiple times. Other Mentions: Dragon Ball Z. Dragon Ball Super. Kino's Travels. Scrapped Princess. Higurashi. Charlotte. Inuyasha. The Devil Is A Part Timer. Grimoire Of Zero. Thanks Mary Ribourg