5. Hellsing (original series)
While the Hellsing franchise has gotten significantly more mainstream since Hellsing Ultimate (an ova reboot), the original anime is still pretty unknown to most people. The plot of the show is dramatically different from the manga at around episode eight. This isn't because the writers were lazy, it's merely due to the fact that the manga wasn't finished (and wouldn't be until 2009). Still, Hellsing is hella fun, with most scenes centering around monsters killing monsters. The main protagonist (note I didn't say hero), Alucard, is the most powerful vampire in existence, and his bloodletting of the various undead is directly proportional to how entertaining the show is.
4. Blue Gender
Blue Gender is basically The Walking Dead: The Anime Version. The story focuses on a young man named Yuji Kaido, who suffers from a rare and puzzling illness. He is an enigma to the medical community in his own time; therefore Yuji undergoes cryogenic hibernation in hopes of a brighter future. When he awakes decades later, the proverbial gates to Hell appear cast wide open. Giant, mutated bugs called "The Blue" have swarmed over the Earth and have ravaged mankind. Some humans have escaped to the stars, where they live on orbital space stations and plan how to regain their place in the world. The show features characters living on the brink of extinction, with every episode a question of survival. Put simply, if you like a character, he's probably going to die.
Monster might be the most realistic anime I've ever seen. Honestly, I sometimes forget that it's animated. Personally, I like anime with a little levity and some colorful imagination. Still, Monster is a hair-raising thriller from the get-go. The anime opens up with a young boy in critical condition. Dr. Tenma, a good-natured doctor, decides to save the life of the child instead of operating on a wealthier adult patient. That decision costs him his career. Yet the higher-ups of the hospital are suddenly murdered, and in their absence Tenma soon moves up the hospital's ladder to become director. Is the boy that Tenma saved truly as innocent as he appears? Is something sinister afoot? Watch to find out!
2. Ronin Warriors
Ah, Ronin Warriors, the forgotten action anime. If you get a kick out of Dragon Ball Z and Yu Yu Hakusho like I do, then you'll find yourself at home here. Ronin Warriors was actually one of the first anime shows aired in America on Toonami, dubbed by Ocean Group (the studio that originally did the voicework for DBZ). Yet after a brief run of popularity, it quickly faded into the vaults of Cartoon Network, never to be seen again on either tv or dvd. Ronin Warriors features sweet samurai combat, coupled with eye-tickling power-up sequences. It also has one of the coolest "shout-out" attacks, with Anubis', "Quake with fear!" line stealing the show.
Mushishi was destined to become obscure as soon as it was produced. Mushishi features no crazy action or evil bad guy with his shadow looming over a city; it's just an anime about nature. The main character, Ginko, is a travelling "Mushi Master", which consists of him encountering various ghost-like entities and their interactions with the natural order. It's never too intense, and the lush green hues of the show make me calm. There is an argument to be made that the series is spiritual as well, as it recognizes the sacredness of the cosmos. Basically, if you think all anime is like Pokemon, then try Mushishiit's pretty chill.