Well you probably have seen Fullmetal Alchemist already, so this suggestion is not very valuable. If you like intense fights and don't mind excessive violence you can try Baccano or Hellsing OVA, those are relatively short, about 10 episodes each, and they are pretty well done. Baccano is a story that takes place in 1930s US, mostly realistic, but with a little touch of supernatural. Hellsing is a vampire story. Both of them are on a verge of being horror shows, but they aren't really trying to be scary.
If you want something with less blood and more good humor you can try Lupin III: The Castle of Cagliostro, witch is a movie done by Miyazaki, it is story about a thief trying to help a certain girl. It is very entertaining to watch, though the movie is like 35 years old, so the art style and animation would look quite different from what you normally see in modern shows.
But if you wanna something that is just like OP, Naruto or Bleach - meaning shonen fighting shows - there are Fairy Tail, Hunter x Hunter, Yu Yu Hakusho, Dragon Ball, Soul Eater. Shaurya can give you better recommendations here that I can, she has seen way many shonen shows than I have =)
By the way, did you are try watching sci-fi anime? They actually tend to be pretty good, if you find ones that are done right. I am watching Psycho Pass now and this is pretty great show.
