Shikamaru

As a Genin, Shikamaru Nara was the sort of unenthusiastic kid who likes watching clouds. He prefers not to get involved in types of "troublesome" situations as during the attack on Konoha by the Sunagakure and Otogakure villages where he pretends to be unconscious. He is fully aware of this side of his personality and even named himself "The number one at running away" or "The number one coward". In fact, his most-used phrase is "How troublesome" in the Japanese version and "What a drag" in the English version. However, when duty calls, Shikamaru has a strong moral compass and sense of commitment to his comrades. Even though by his own testimony he lacks bravery, he will sacrifice himself and face almost certain death for the sake of his friends or villagers without a second thought, such as when he stayed behind to confront a team of Sound ninjas, giving Naruto enough time to catch up with Sasuke. In short, he is the very definition of how a leader should be like and it is for his raw leadership skill why he was the first genin from the rookie 9 to become a chunin.
Shikamaru has a longstanding friendship with Choji Akimichi, in whom he has complete trust with. Before they were promoted to Chunin rank, Shikamaru, Choji and Ino Yamanaka were on the same Genin team under Asuma. Their fathers were on the same team as well. Their teamwork is unparalleled. They are the next generation of Ino-Shika-Cho trio, which is fully compromised from their past ancestry.
Shikamaru loves to play thinking games that older men are usually into, such as Shogi and Go. He is a brilliant strategist, and though his sensei, Asuma Sarutobi, often plays against Shikamaru, Asuma has never actually managed to beat him. Asuma got suspicious upon realizing that Shikamaru was so good at board games despite his abysmal grades, which were almost as low as Naruto's. As a result, Asuma administered an IQ test disguised as a game to Shikamaru, which revealed that Shikamaru was beyond a genius with an IQ of over 200. Shikamaru had felt that even moving his pencil in class was a bother and always slept through tests, resulting in his low grades. Nevertheless, his great wisdom and strategic expertise balanced his shortcomings.
Shikamaru has a habit of putting his fingers together to create a circle and closing his eyes so he can concentrate and come up with a strategy. Once he does, which often takes only a few minutes, he is able to think ten moves ahead of his opponent with over a hundred strategies ready to be used, even being able to plan out "the next 200 moves in advance". This hand sign intimidates the opponent, making them believe that he has an ace up his sleeve while in actual fact it just buys him time.
Since he has been promoted to Chunin, his responsibility for the lives of his friends has weighed very heavily on him on occasions. These burdens have also revealed his great maturity evolving over time.