The sniper monkey is a slightly expensive tower that has infinite range (not always the case as that can be incorrect if you're playing certain levels in BTD 6) that can hit any bloon on screen, except for camo and lead bloons if the sniper doesn't have the right upgrades to damage those. A sniper can be upgraded for more damage per shot, higher fire rate, and can stun MOAB class bloons with the "MOAB Cripple" upgrade, allowing them to give others towers a bigger oppurtunity to elimate them.