Tesla Turret is an incredibly strong variant of Defense Turret that fires explosive electric projectiles. It has long range. Its chances of hitting a moving target are average (it's not as bad as Rocket Turret, but it's not stellar either).
The weakness of this turret is that its projectiles are a threat to player-built structures (they can damage the blocks), so it might not be a good choice for protecting an NPC town (unless it's built from durable blocks).
Defense Systems (Electronics tree).