Resident Evil: The Mercenaries 3D has a Skill Slot customization feature. You can fill three skill slots from a selection of 30 skills, including improvements to weapon performance, reload speed or melee abilities.
You can take a look at that feature in the new trailer in this post. Capcom have included 30 missions in The Mercenaries 3D, and you unlock new skills along the way.
The Mercenaries 3D scheduled for release sometime this summer. The game will also include a demo version of Resident Evil: Revelations.