You can find articles on all of these [except for Yugo the Negotiator] on Wikipedia.
Gankutsuo: The Count of Monte Cristo--It's basically a loose retelling of the original story in a futuristic setting, but the Count is depicted as being a lot darker in this series. It has some of the most detailed artwork you will ever see in any sort of animated series/film. Production value is top-notch.
Full Metal Panic!--a good mix of military action and comedy. Full Metal Panic? Fumoffu is a collection of side stories that focuses on the comedic aspect of the first series. Full Metal Panic: The Second Raid continues the storyline of the first series. There are tons of parodies (like Full Metal Jacket, Monty Python, Forrest Gump), particularly in FMP? Fumoffu.
Vampire Hunter D: Bloodlust--kinda self-explanatory here. Tons of really cool action sequences, great voice acting, highly detailed, dark artwork and character design, and an interesting story. A really great movie all around.
Zipang--"A Japan Maritime Self-Defense Force Yukinami-class Aegis escort vessel, the JDS Mirai, while enroute on foreign dispatch is timewarped to the Pacific Ocean just prior to the Battle of Midway of World War II. After rescuing an Imperial Japanese Navy commissioned officer, Takumi Kusaka, the Mirai and its crew go on to affect the course of history itself." (wiki) Highly recommended for anyone who likes war movies.
Yugo the Negotiator--a series that describes the adventures of a hostage negotiator in Pakistan. A lot of attention is paid to accurately depicting this [real-life] job and the local culture.
Witch Hunter Robin--This one is somewhat self-explanatory, although it does not constantly focus on action like other similar series; rather, it has more of a relaxed, more realistic feel to it, which is a nice change of pace. The "hunting" of witches operates more along the lines of investigative police work, kinda like CSI.
Gungrave--follows the life of Brandon Heat as he joins the local mafia, climbs up the ladder, and is later betrayed and killed by his best friend, who becomes the leader of the mafia. 13 years later, Brandon is reanimated and seeks revenge against the organization. A very serious, but enjoyable, series.
Ah! My Goddess--a romantic comedy series that is not too mushy and doesn't have tons of fanservice like most others in this genre. It's a pretty light-hearted series; even when things do get serious, they throw in some humor to break things up. Ah! My Goddess: The Movie is excellent as well. The Norse mythology elements are pretty neat too.
RahXephon--my favorite mecha-related series out there, although the "mechs" aren't mechanical; they're clay golems which have a symbiotic relationship with the person (or alien) that controls them. It's pretty unique in the sense that it's not a simple story of galactic conquest or defending Earth from mindless hordes of aliens. "The overarching theme of RahXephon is one of music changing the world." (wiki)
Blue Gender--pretty similar to Starship Troopers, except that the origins of the insectoid aliens are not what you would expect.
Chrono Crusade--follows the adventures of a teenage girl nun and her partner (who is a demon) as they go around killing other demons that threaten society. It takes place in the 1920's. There are all sorts of cool sections about the time period in the extras.
Saikano--a tragic romantic series (there's an OVA too). It follows the struggles of a high school couple as the girl is turned into the ultimate weapon by the government and becomes less and less human the more she fights in the war. This is a highly involving, sad, and depressing series; so much so that some people cannot stand watching it a second time through because of how immensely sad it is, especially when it gets close to the end. But if you think you can handle it, then go for it. This is a must-have series for me, even though I could barely handle it myself at times. It is definitely worth getting.
Gankutsuo: The Count of Monte Cristo--It's basically a loose retelling of the original story in a futuristic setting, but the Count is depicted as being a lot darker in this series. It has some of the most detailed artwork you will ever see in any sort of animated series/film. Production value is top-notch.
Full Metal Panic!--a good mix of military action and comedy. Full Metal Panic? Fumoffu is a collection of side stories that focuses on the comedic aspect of the first series. Full Metal Panic: The Second Raid continues the storyline of the first series. There are tons of parodies (like Full Metal Jacket, Monty Python, Forrest Gump), particularly in FMP? Fumoffu.
Vampire Hunter D: Bloodlust--kinda self-explanatory here. Tons of really cool action sequences, great voice acting, highly detailed, dark artwork and character design, and an interesting story. A really great movie all around.
Zipang--"A Japan Maritime Self-Defense Force Yukinami-class Aegis escort vessel, the JDS Mirai, while enroute on foreign dispatch is timewarped to the Pacific Ocean just prior to the Battle of Midway of World War II. After rescuing an Imperial Japanese Navy commissioned officer, Takumi Kusaka, the Mirai and its crew go on to affect the course of history itself." (wiki) Highly recommended for anyone who likes war movies.
Yugo the Negotiator--a series that describes the adventures of a hostage negotiator in Pakistan. A lot of attention is paid to accurately depicting this [real-life] job and the local culture.
Witch Hunter Robin--This one is somewhat self-explanatory, although it does not constantly focus on action like other similar series; rather, it has more of a relaxed, more realistic feel to it, which is a nice change of pace. The "hunting" of witches operates more along the lines of investigative police work, kinda like CSI.
Gungrave--follows the life of Brandon Heat as he joins the local mafia, climbs up the ladder, and is later betrayed and killed by his best friend, who becomes the leader of the mafia. 13 years later, Brandon is reanimated and seeks revenge against the organization. A very serious, but enjoyable, series.
Ah! My Goddess--a romantic comedy series that is not too mushy and doesn't have tons of fanservice like most others in this genre. It's a pretty light-hearted series; even when things do get serious, they throw in some humor to break things up. Ah! My Goddess: The Movie is excellent as well. The Norse mythology elements are pretty neat too.
RahXephon--my favorite mecha-related series out there, although the "mechs" aren't mechanical; they're clay golems which have a symbiotic relationship with the person (or alien) that controls them. It's pretty unique in the sense that it's not a simple story of galactic conquest or defending Earth from mindless hordes of aliens. "The overarching theme of RahXephon is one of music changing the world." (wiki)
Blue Gender--pretty similar to Starship Troopers, except that the origins of the insectoid aliens are not what you would expect.
Chrono Crusade--follows the adventures of a teenage girl nun and her partner (who is a demon) as they go around killing other demons that threaten society. It takes place in the 1920's. There are all sorts of cool sections about the time period in the extras.
Saikano--a tragic romantic series (there's an OVA too). It follows the struggles of a high school couple as the girl is turned into the ultimate weapon by the government and becomes less and less human the more she fights in the war. This is a highly involving, sad, and depressing series; so much so that some people cannot stand watching it a second time through because of how immensely sad it is, especially when it gets close to the end. But if you think you can handle it, then go for it. This is a must-have series for me, even though I could barely handle it myself at times. It is definitely worth getting.