If you liked the Black Lagoon: Roberta's Blood Trail anime, the Anime-Planet community thinks you'd like:
Follow interstellar bounty hunters Spike Spiegel and Jet Black as they scour the galaxy for criminals with prices on their heads. Hoping to escape their past, they live on the spaceship Bebop, but it's a dangerous business and old enemies don't forget easily. Allies come from unlikely sources, however, as they find comrades in the beautiful swindler Faye Valentine, the genius child hacker Ed and the genetically engineered 'data dog' Ein. Will they be able to help each other though their respective struggles, or is their fate really inevitable?
Cowboy Bebop, like Roberta's Blood Trail, is set in the criminal underworld. It promises plenty of revenge stories, battle-hardened characters, and tragedy, along with the pretty glorified violence of course! Bebop will be slightly less bludgeoning fare and more sophisticated character development (especially where Spike is concerned), but for more tales of people lost in the limbo of criminal life, check out Bebop.
Brandon Heat and Harry MacDowel were best friends who lived by the law of the street, until one day they picked a fight with the wrong people and their life of freedom was suddenly taken away. With no one to turn to and nowhere to run, the choice to join Millenion, the city's most powerful syndicate, seemed like an offer they couldn't refuse. Now, amidst heartache, tragedy, and utmost betrayal, Brandon must take up the gun and help Harry climb the ranks of Millenion to succeed, in order to protect the people he loves, even if it means killing countless others in the process.
Gangsters, tough talk, guns and more guns. Gungrave, like Roberta's Blood takes a gritty appraoch where blood and betrayals are aplenty and the world is an unforgiving place to those who don't watch their backs. One thing to note about Gungrave is that it tacks on some science fiction while Black Lagoon remains firmly set in realism. The general gist, however, is very much the same.
Alucard is a vampire who works for Hellsing – an organization responsible for hunting down and destroying other vampires. In these dark times, whoever is bitten by a vampire turns into a ghoul -- with the exception of Seras Victoria, Alucard’s newly created and appointed apprentice. Now, Seras must serve her master, Alucard and work for Integra Wingates Hellsing. Nefarious vampire activities are being reported throughout England, and it all traces back to the organization named “Millennium”. Will the Hellsing organization, under the command of Sir Integra Wingates Hellsing, be able to prevent a full scale war? Or will the world become a battlefield of destruction?
What does Black Lagoon OVA and Hellsing OVA have in common? Psycho characters, lots of action and over the top violence. If you liked one of those, you got to check out the other one.
P.S. Be sure to watch both seasons of Black Lagoon TV, before watching Black Lagoon OVA.