I'd NEVER use that!
Just kidding.
My problem with some of the D20 Modern firearms Feats is that they make feats out of things that anyone who gets some firearms training can do. I think of double-tap as a basic firearms rule, not a feat. If you want I will post some of my firearms house-rules but for me, anything related to rate of fire is rule-based not feat based. This goes for rapid fire, covering fire, cyclic (auto) fire and scope / bipod / mount / use. This is all party of the Firearms Proficiency Feat.
Gun manouvers are a whole other thing though. Guntouchable (Nice) and Rapid reload are groovy and trick shot feats like skip shot can suit if it goes with the style of the game. Other useful ones would relate to running and gunning, squad zonal shooting formations and Contact drills (ie squad / fireteam manouvers that are performed based on a certain kind of contact) Eg: `Contact Left': The SAW gunner and his ammo feeder anchor the team, laying down cover fire as everyone fans out to one side and the radio operator gets on the horn for support. The team gets a +2 bonus against intimidation or for a morale check.
Even if you aren't going for a military themed game there are plenty of possible manouver feats for 2 man teams or for solo gunning. Police train for 2 and 3 man manouvering and obviously SWAT style teams train for CQB. The kinds of bonuses that these Feats can give relates to improved defense (harder to hit), initiative bonuses (team awareness and communication), higher intimidation "Freeze Mofo!", flanking bonuses, communication and planning bonuses (try imagining putting together a plan and communicating it to a team-mate when someone is shooting at you, pretty hard without practice) and bonuses (or negated penalties) for coordinating fire and manouver with a team mate who you cannot necessarily see or talk directly to (relates to contact drills).
Anyway, that's my .45 worth.
Matterhorn.
Matterhorn is a collective of 500 echidnas with laptops sealed in a bunker beneath the Melbourne Cricket Ground.