6. Hawkeye
Although Hawkeye was an integral part of the plot in the Avengers movie, he wasn't really Hawkeye for most of it (having found himself to be under Loki's control and working against his team-mates as a result). That said, whilst under Loki's control, and indeed in the final battle of New York when he was actually fighting for the forces of good, he displayed some crazy skill. He used a specialised bow made specifically for his arrows. It came with a quiver to house the numerous arrows, was mechanized and could swap arrowheads such as standard projectile arrows, explosive arrows, arrows with electrical devices attached to them or grappling hooks. Simply pressing a button on the handle grip of the bow made an arrow combine with the selected specialised arrowhead. It was also foldable, as seen when Hawkeye is in Loki's underground base when he's retrieving it from his case. Hawkeye is extremely proficient in its usage and can be accurate with his aim even when he's not looking at his target, such as when he took out a Chitauri flier just by hearing it behind him. The fact that he can use it as well as most people use automatic weaponry is testament to his skill and he was clearly a proficient hand-to-hand fighter as well - taking out several Chitauri soldiers with relative ease.