Umm, that's a real hard one, espacially if you've seen a lot of different anime, so i'll start with the manga as there are only a few i've read. I'll just consider those i bought, so this is a short list:
1. Shingeki no Kyojin (Aka. Attack on Titan)
2. Gokukoku no Brynhildr (Aka. Brynhildr in the Darkness)
3. Accel World
4. Ousama Game
5. Death Note Stopped after buying the seventh chapter though, because i did not like how the story developed after one certain point. (Trying not to spoil here >.>)
Now about Anime. Anime is a lot harder, but i'll try my best. These will only be in somewhat of a specific Order as i can't really say which one is "higher up"
1. Mirai Nikki - It's a great Anime even though the protargonist can get really annoying throughout the Anime, but Yuno definitely compensates for that!
2. Another - Even though it's a more bloody Anime, it definitely has one of the best Stories and Charakters i've seen in a long time.
3. Angel Beats - I don't really know what to say about Angel Beats, besides that it left me crying for several hours after it ended >.>
4. Parasyte - This Anime. It's just.. so good. And the message.. WOW. The Soundtrack as well! Still listening to it c:
5. Zankyou no Terror - This is another one of those Anime which i could watch over and over again and still be amazed by the Story, the Charakter development and everything. This one is beautiful.
Honorable Mention: Digimon (Entire Series) - How could i make a favorite Anime list without mentioning Digimon? Digimon was just one of these Series which just made my childhood my childhood. I used to rewatch entire Seasons (except the fourth one. Fourth one was meh), even as i got older. Just last year i watched the entire third season in one go, just because i freakin love Digimon
Hope noone minds me posting in this kinda dead Topic ^^ But i really did not want to open a new one if one already exists c: