Well then... Here's some more:
Ciguatera may fit what you're looking for then (but you have to read it to the end).
Marie no Kanaderu Ongaku had some weird plot twist at the end IIRC.
Mon Seul would fit but pedophilia is a "NOPE!" from me.
Homunculus had innuendos

OK.
Im gonna round up all the suggestion :
Ichigo 100% already read
Usagi Drop already read
Mon Seul 1 vol, done reading, upset with the epilogue, kinda hoping for

incest ending

waiting list:
School Days 2 vol
Marie no Kanaderu Ongaku 2 vol

longer waiting list:
Honeymoon Salad 5 vol
Ciguatera 6 vol
Moe Kare!! 7 vol
Cat Street 8 vol
Yubisaki Milk Tea 10 vol
Otaku no Musume-san 11 vol
Homunculus 15 vol

Like we could see, Im sorting my list with order of number of volume
Because I think its better to read 10 manga title with each 1 vol, than 1 manga title consist of 10 vol or more.
Im still stuck at 1&2 vol manga waiting list. And because of it, I end up alot with manga that was rushed ending/axed.
Oh, but for Oneshot, I only pick whats interesting. There are to many oneshot out there....
Only occasionally I skip my list and choose some manga that was really interesting so it could make me skip my own list.
I've done this to Ichigo 100%, Onani Master Kurosawa, Adachi Mitsuru work, Kano Yasuhiro work and YOKO work.