There's Squall from Final Fantasy VIII that uses a gun blade, I haven't played it so I'm not sure how they implement it though.
The Disgaea series is a Turn-based RPG where you can create loyal minions to help do your selfish, greedy, personal bidding. There's two classes that uses guns as there main weapon, the Scout and Thief, so you can have infinite Thief's mugging other demons, and Scouts can control the terrain to map out an easy kill, but you can only have ten characters on a map at a one time... These are just the guns portion there is must more classes to be discovered. Oh and did I mention that you can go as high as level 9999 and do over a million damage? (not kidding)