Lets see since I read a ton of manga here are some that you might not know that are really good:
Voynich Hotel is fantastic, random, and weird as hell. Sort of 18+ but thats ok
Animal Land or Doubutsu no Kuni starts off fairly lighthearted and fun but gets really, really hardcore as it goes on.
Can't find the MyAnimeList link for it, but one of the best anime/manga of all time Corey in the House. 11/10 storytelling and great and memorable charachters.