In the early 21st century, the emergence of an incurable condition known as B-cell growth led some of the affected to become "Sleepers" - people put under stasis until a cure could be found. Yuji Kaido is one such Sleeper who awakens, several decades later, to a horrifying new reality. Giant bugs known as Blue have invaded the Earth, eating everything - and everyone - in sight. Now, all Yuji can do is escape from the city with the ones who saved him from his inevitable death, and make their way towards Second Earth: mankind's new home in space.
A devastating earthquake strikes Tokyo, leaving the city in ruins. Man's only hope is to use boomers, an artificial humanoid form. Everything seems perfect until some of the boomers go crazy and start killing people. The only hope of stopping them is the Knight Sabers, a group of 4 female heroes in form-fitting power suits, with which they can perform amazing feats of strength and agility.
Like most boys his age, the young Renton thinks of nothing but reffing – riding trapar waves on a board – and idolizes Holland, the leader of the renegade group of reffers named Gekko State. As an orphan of a famous hero, he lives a boring life with his grandfather until the beautiful Eureka crashes, literally, into his life. Now, with the help of his newfound friend and crush, Renton finds himself living amongst the crew of Gekko State. The errands are hard and the bullying is fierce, but with Eureka by his side, Renton just might find the courage to tough it out and even save the world!
Two major world powers have constructed the most dangerous weapon on earth: Tactical Armor (TA), an elite fighting mecha with extreme agility and fighting strength. Yushiro Gowa is the top TA pilot and captain of the Japanese Self-Defense Force, an orginization that uses the TAs to try and bring honor back to Japan. Yushiro must make a hard decision and face the truth about his past and the secrets of the Gowa family, who will use their adapted spiritual powers to summon Gasaraki and unleash terror on all of mankind.
A world torn apart by a war that faces a new terrible weapon, the Tactical Armour. Both anime's have been done by the same author so you know the quality ;)
Mecha's are realistic and have a real good technology output that gives it that... 'realistic feel' that lacks in many other anime.
For me it's a must.
In the early 21st century, insectoid organisms are invading the galaxy, searching for new stars to house their young. Mankind's only defense lies with space cadets such as Takaya Noriko, daughter of a celebrated admiral killed in battle, and Amano Kazumi, the top of her class. With their skill and the power of the mecha known as GunBuster, the girls must help fight to protect the galaxy from total annihilation...
Both of these shows have to deal with Mecha robots and aliens that want to destroy the planet Earth. Blue Gender is how the alien life forms took over the planet and the military is trying to take it back, but will they ever succeed? And GunBuster is about war with space aliens that are trying to get to plant earth, but will they get there? Both shows are filled with action and adventure and both have great story's.
Also There is Gunbuster2 but is different story from than first one.
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.
Both of these anime are dark, depressing, and morbid, with a well-developed plot and a strong, coherent story arc. Blue Gender is more sci-fi, where Gungrave is more of an alternate present; but while both are quite dramatic, don't expect to walk away from either one with a smile on your face.