On the off chance you haven't seen it already,
Mahou Shoujo Madoka★Magica (2011) would be highest suggestion, it's great overall series with an excellent ending, the single best Magical Girl series since Nanoha for me easily
.
Or the recently finished
Shinsekai yori(2012-2013), it's mysterious yet very compelling with a very solid ending to it.
Or looking for something a just
little bit less dark than the above series,
Steins;Gate (2011) a series dealing with the potential of time travel and potential alternative time lines with a very strong ending to it.