Iron sights, both eyes open, put the front post center of mass, absolutely fastest way to acquire something room-to-room. If you want an optic for CQB, then I'd say the Leupold DeltaPoint, or the Trijicon RMR. I have one on my DSA TP9 SBR and its faster than swinging a glock 34 onto a silhouette. For CQB to short/medium range, the Eotechs and Aimpoints reign supreme.
Just remember that all the guys shooting 3-gun with 30mm toilet paper tube optics are shooting most courses of fire between 20-100 meters.