Ill update this list if it gains interest. Im a huge fan of anime, of all sorts. Here are a few off the top of my head that i greatly enjoyed, but arent really mainstream. In NO particular order.
1. Guilty Crown - this anime is 22 eps. It starts a bit slow in terms of digging into the REAL plot. But once it does, you cant tear away. Its very well done in terms of presenting plot in a way that keeps you interested. And its a good plot, i enjoyed it.
2. Puella Magi Madoka Magica (aka Magical Girl Madoka) - ok, this one is 12 eps. You absolutely must ignore the lightheartedness in the first few episodes. this is a relatively deep and violent anime. The title makes it seem like its something it isnt, those japanese folks have a weird way of doing things. Im not giving reviews or details to this stuff. Im just telling you, watch it. You will come to understand beginning at the end of EP3. It onky gets crazier from there.
3. Another - If you like horror and creepiness, this ones for you. I love this anime. DONT go in expecting a bunch of fighting it doesnt exist. There is gore and violence (sort of..). But its more of a creepy ass story than anything.
4. Deadman Wonderland - So Adult Swim is now showing this 12 ep anime. Meh, find an uncut version online. Its a great anime and one of the most sadistic ideas ive ever seen. Dont watch adult swim version.. just dont. Im sure its good, but youre missing the core feeling of it.
5. Angel Beats - This anime is 12 eps(i think..it isnt long either way) and a good one. Im not going into much here. Its not at the tippity tip top of my list by any means, but its a good watch.
6. Death Note - This may be mainstream but i swear everyone i ask has never heard of it. THIS IS ONE OF THE MOST INTRICATE AND INTRIGUING STORIES IVE EVER SEEN. Its a work of art. That simple. Idk how many eps, 35 or so i think. Its a psychological-thriller. If you have ANY interest i that kind of thing. WATCH THIS. nuff said.
If anyone cares to add to this feel free, of any suggestions. Most mainstream anime is okay, and some is really really good. But theres sooooooo much that never gets seen because it isnt advertised and pumped up, that is just so damn good.