Just gave my friend a big list of stuff he should watch so I'll just post it, ones in old are my favorite and the best series ever in my opinion, I'll explain in more detail about the series if you ask, not doin' it automatically cuz dere so many D::
Level E (current series)
Sayonara Zetsubou Sensei
Higurashi no Naku Koro Ni/Kai/Rei
Umineko no Naku Koro Ni
...Any Gundam you havent seen besides the SEED and Wing series'
Welcome to the NHK!
Legend of the Galactic Heroes (super duper long, but supposed to be fantastic)
Combat Mecha Xabungle (subs arent quite finished yet, but theyre still going)
Kore wa Zombie desu ka?
JoJos Bizarre Adventure (my favorite manga, fourth part has a terrible scanlation but its getting redone; you can get the gist of it tho)
Kamen Rider Spirits (second favorite manga)
Welcome to the NHK! (mangas fairly different from the anime)
Stone Ocean (another part of JJBA)
Steel Ball Run (same as above)
Kinnikuman (crazy wrestling manga)
Ultimate Muscle/Kinnikuman Nisei (sequel to Kinnikuman)
20th Century Boys (by the same guy as Monster, being released in the US, but I dont like some of their translation choices, but it's sooooo gooood)
Sayonara Zetsubou Sensei (being released in the US)
Dorohedoro (being released in the US)
Bokurano (being released in the US, pretty different from the anime I think)
Manga: Vinland Saga (VIKIIIINGS)
MONSTER (SO GOOOOOOD)
Pluto (by Monster guy)
20th Century boys (don't remember if I said this one)
Billy Bat (his latest work)
Manga: Franken Fran (bloody)
Transformers Galaxy Force (sweet voice acting)
GaoGaiGar (so awesome) (so manly, giant robots, so awesome)
Anything out of the Brave Series basically.
All I can remember, you might not like all of them, my suggestions are tailored to what me and my friend like (IE: Robots and ACTION)