There are a couple "3x" magnifier units now becoming available which can be mounted just behind an Aimpoint or EOTech, yet be quickly flipped out of the way when not needed. These can help with target ID, however, they have a much narrower field of view than true magnified optics (Type II and III).
Type II: low-power magnified optics with reticle features for bullet-drop compensation when engaging targets outside of the cartridge's point-blank range. External and non-capped target knobs/turrets should be avoided to ensure the zero is not lost when the knobs get bumped, hit, or rub on other gear. Type II optics are designed for quickly engaging targets from about 75 yards out to about 400 yards. Many Type II optics are fixed magnification at 3.5x or 4x, however, several variable power 1 - 4x scopes are also in use. The most common is the Trijicon ACOG: 4x (TA31, TA01) or 3.5x (TA11). The US Military realizes many of these needs in the Designated Marksman Rifle (DMR) and Squad Designated Marksman Rifle (SDM-R).
# 2. The Trijicon TA11 ACOG is a compact and durable Type II optic optimized for quickly engaging multiple targets from 75 to 400 yards.
Of the fixed-power Type II optics, the TA11 ACOG is the best choice. It provides a little more eye relief and a large exit pupil than the TA01 and TA31. Together, these two attributes make it a lot faster to acquire a sight picture and easier to maintain while on the move. The 0.5x difference in magnification versus the TA31 is marginal. Price on a TA31 or TA11 ACOG with a QR mount is about a grand. The Schmidt and Bender 1.1-4x20mm Short Dot has almost true 1x at the low and a bright illuminated reticle center. It has a mil-based reticle for bullet drop, in addition to external target knobs (the locking turrets are the way to go for reliability). The extra capability of the Short Dot is paid for in bulk and its $2200 ticket. The sleeper is the 1.25-4x24mm Trijicon AccuPoint (TR21). It shares the same fiber-optic design as the TA31/TA11, but can be dialed down to low power for close-range work. Its reticle has no BDC features, however. The TR21 is a good deal at about $575.