 If you liked Hellsing |  ...then you might like Gantz |
I dont know what people think of Hellsing and Gantz but to put them both in a nut shell. gore, more gore, and destruction. Hellsing is a Alucard killing off his own kind (vampire) and Gantz is a group of people killing aliens. Both have very detailed story lines. Gantz would be a little more gory because there is more fighting involve but Hellsing is a great way to laugh (depends on how you like gore).
Both centre around a fantasy/supernatural/not-quite-normal element kept secret in an otherwise mundane, relatively true-to-life world, and a great deal of bloody, gory violence.
report Recommended by lithiumflower
To make this simple, Hellsing and Gantz contains violence, gore, and lots of everything else that you find in a good action manga. These two are not like the ordinary manga you read, to only reinforce the idea that they share similarities. Kei [Gantz] and Alucard [Hellsing] are somewhat similar b/c over many chapters they change and able to show their real power. Not to mention they have similar art and a story with much unexpected turns. Another note to consider is both series are produce by Gonzo.