Greyah said:
I just finished watching Gunslinger Girl. Though the ending was a bit sad, I loved it.
Apparently there is also a second season, but I'm not sure if it's as good as the first.
The only similarities the first has to second is the setting, the characters and the general idea (little girls murdering terrorists). Otherwise, it's pretty different: new art style, different music, more a focus on the fights and new characters. I think they even switched the voice actors in the dub (which is still pretty good).
Honestly, I liked the second one a little more than the first, since they gave the terrorists faces and names and backstories. However, the ending isn't that good. It's not bad, just so overwhelmingly mediocre.