Lasers

A laser is an aiming aid for the situations where you cannot use sights: an awkward position, a compromised firing grip, or from behind cover. What it is not is a substitute for sights, and using it as one builds a habit that fails the moment the battery does.

Green lasers are far more visible in daylight than red ones, at greater cost and shorter battery life; red runs longer and is mostly an indoor and low-light proposition. Either way, zero it at a realistic distance and understand the offset — the laser sits below or beside the bore, so it converges with the point of impact at exactly one distance and is off everywhere else.