What I mean by borderline is something similar to Futari Ecchi and Buttobi CPU. They have sex as the center, but you never really get the full effect and they're absolutely hilarious. I don't really want a full blown hentai with blowjobs and rape (absolutely not), but will take a hentai as long as it'll make me laugh my ass off and is interesting like Hatsu Inu; doesn't get more interesting than a vibrator obsession if you ask me. Also, no loli please.
Note: something short is preferable as well (6 eps or under) because too much ecchi and sex can get stale for me. I'll take a maximum 12 eps but only if it's hilarious every episode and doesn't dull down in the later half.
Kuronoa said: Kanokon was the first thing that came to mind.
Yes, there is no anime that can be ecchier than that, although for me, it's nowhere near hilarious. Kiss x Sis is also epic, if only I had sisters like that... I don't really recommend watching Green Green, it just isn't good enough. If you can laugh at how the hell does the clothes get destroyed in every single fight, try Ikkitausen, or it's less ecchier version Tenjou Tenge. Rosario + Vampire also has it's merits, but I somehow like the manga more than the anime.