Many of the towers are either monkeys, units maintained by a monkey, or units owned by a monkey, with the exception of the Tack Shooter, Bomb Tower, Ice Tower (in BTD4), Spike Factory and Banana Farm (unless upgraded to Monkey Bank).
Hotkey: Q Description: Shoots a single dart that pops a single bloon. A good, cheap tower suitable for the early rounds. Ability: Super Monkey Fan Club Ability: Converts up to 10 nearby dart monkeys into Super Monkeys for 15 seconds.
Hotkey: W Description: Shoots 8 tacks spread in all directions, each tack can pop 1 bloon. Has short range and medium-slow fire rate. Ability: Blade Maelstrom Ability: covers the area in an unstoppable storm of blades.
Hotkey: T Description: Stealthy tower that can see Camo Bloons and throw sharp shurikens rapidly. Ability: Sabotage Supply Lines Ability: Sabotage the bloons supply lines for 15 seconds. During the sabotage, all recently created and new bloons are crippled to half speed.
Hotkey: Y Description: Shoots a single bomb that explodes in a radius burst on impact. Good range, medium-slow fire rate. Can pop lead bloons but not black bloons. Ability: MOAB Assassin Ability: super deadly missile seeks the nearest MOAB-class bloon and destroys it instantly. Does 1000 damage to ZOMG bloons instead of destroying them.
Hotkey: A Description: Freezes bloons in its burst radius for a short time. Frozen bloons are immune to sharp objects. Ability: Absolute Zero Ability: freezes the entire screen of bloons for 4 seconds. Does not affect MOAB-class bloons.
Hotkey: D Description: Monkey Buccaneers can only be placed on water. Shoots a single, heavy dart that can pop up to 5 bloons each. Ability: MOAB Takedown Ability: takes hold of the nearest MOAB-class bloons with a grappling hook and brings it down. ZOMG bloons are immune to this.
Hotkey: F Description: Patrols the skies above the action, regularly strafing the area with powerful darts in 8 directions. Ability: Drops a single devastating bomb that destroys all bloons on screen and heavily damages MOAB-class bloons. Several bombs needed to take down a ZOMG.
Hotkey: G Description: Throws darts incredibly fast. Has long range and lots of insanely powerful upgrades. Ability: Be proud of this Technological Terror you've constructed. Bloon Annihilation Ability: Destroys all bloons within short radius of tower, completely and utterly. Does 1000 damage to MOAB-class bloons.
Hotkey: H Description: Trained in the arts of monkey magic, the Monkey Apprentice weaves magical bolts of power that can pop bloons. Each shot can pop 2 bloons. Can upgrade to cast additional spells. Ability: Summon Phoenix Ability: Creates a super powerful flying phoenix that flies around wreaking bloon havoc for 20 seconds.
Hotkey: C Description: Monkey Village does not attack bloons but instead lowers cost of all towers and upgrades in radius by 10%. Has many useful upgrades that help nearby towers. Ability: Call to Arms Ability: Doubles the attack speed and popping power of all nearby towers for 10 seconds.
Hotkey: V Description: Banana Farms grow bananas that you can collect to turn into cash. When your farm produces some bananas, collect them by moving your mouse over them. Don't leave them too long however, or they will spoil!
Hotkey: B Description: Targets a specific bit of ground anywhere on the screen. Launches explosive mortar shells to that spot. Useful for placing far away from the track to make room for other towers. Ability: Shoots mortar shells 3x as fast. Pop and Awe Ability: bombards the screen for 5 seconds, popping every bloon 1 time per second and immoblizes all bloons during that time. Does not affect MOAB-class bloons.
Hotkey: N Description: Shoots darts like a machine gun, super fast but not very accurate. The Dartling Gun will shoot towards wherever your mouse is, so you control how effective it is! Ability: The BADS covers a wide area with each shot. Enables the Rocket Storm Ability: Rocket Storm shoots out a missile towards the nearest 100 bloons on screen. Ouch.
Hotkey: M Description: Generates piles of road spikes on bits of nearby track. Each pile can pop 5 bloons, and unused spikes disappear at the end of each round. Ability: Lays down a thick carpet of spikes over the whole track.
Hotkey: J Description: Water based tower that shoots homing darts. Can upgrade to shoot at Bloons in the radius of any other tower. Can also upgrade to submerge and become a support tower. Ability: First Strike Capability Ability: a devastating missile strike on the largest bloon on screen. Destroys up to a ZOMG bloon in one go, or many lesser bloons.
Hotkey: L Description: Good at building stuff, the Engineer shoots bloons with a powerful nail gun and has many useful upgrades that create traps, sentries and other enhancements. Ability: Activated Ability: Overclock - target tower becomes super powered for 60 seconds.
Hotkey: ; Description: Rapidly sucks up and shreds bloons, spitting what's left out the back. Ability: Huge burst of suction power brings all nearby non-MOAB class bloons towards it and holds them there until they have been sucked into the tower. Lasts 8 seconds.
Hotkey: None Description: Powerful attack helicopter armed with twin dart shooters and multiple patrol options Ability: Support Chinook Ability: drops med and cash crates, or can pick up and reposition most towers