Rangefinders

Knowing the range is what makes bullet drop calculable rather than guessed, and past about 300 yards estimating by eye is unreliable for almost everyone. That makes a rangefinder the accessory that most directly improves hit probability at distance.

The advertised maximum range is measured against a large reflective target in good conditions and is not what you will get on a deer in trees at dusk — expect roughly half. The feature worth paying for is angle compensation: shooting steeply uphill or downhill means the bullet only drops over the horizontal component of the distance, and a unit that reports true ballistic range removes that error entirely.