Gargantuan Monkey

The Gargantuan Monkey is a giant monkey (I would have called it Giant Monkey, but there's already a Special Agent with that name) with a club that it uses to smash nearby Bloons. It smashes the ground every five seconds, has a medium range, is as big as a Monkey Village, and pops two layers from the Bloons it hits! The low attack speed limits its usefulness, but it has infinite Popping Power, making it perfect for fighting groups.

It also has 40HP and 3AD!

It would look like a huge Monkey holding a brown club (simple, really).

Longer Club
The Club is longer, increasing range.

Price: $350 on Medium.

Appearance change: The club is longer.

Details: Range increases to 4/2 Village.

Lightweight Club
The club becomes lighter, almost doubling attack speed!

Price: $1,500 on Medium.

Appearance change: The club becomes a lighter brown.

Details: Attacks every 3 seconds.

Wider Club
The wide club can hit Bloons in a larger area!

Price: $3,000 on Medium.

Appearance change: The club becomes wider.

Shockwave
A shockwave stuns Bloons that are hit for two seconds, and nearby Bloons are stunned for one second. Does not affect MOAB-classes.

Price: $7,000 on Medium.

Appearance change: The end of the club becomes metal.

Little Helpers
Tier 5 Upgrade: Eight tiny Monkeys (about half a Dart Monkey's size) surround the Gargantuan Monkey, each has 6HP and is equipped with a tiny club which hits every two seconds, has no stunning effect, and removes one layer.

Price: $8,000 on Medium.

Appearance change: None, except for the addition of the surrounding Monkeys.

Details: They all have the range of a 0/0 Tack Shooter, and you can replace them if they die for a cost of $500 each.

Spiked Club
Pops three layers instead of two!

Price: $750 on Medium.

Appearance change: The club gets spikes on.

Armoured Giant
Increases AD to 5!

Price: $500 on Medium.

Appearance change: The Monkey is covered in armour.

Double Smash
Immediately after smashing, it smashes a second time!

Price: $1,750 on Medium.

Appearance change: Its arms are bigger.

Details: Smashes twice with 0.5 seconds in between smashes. After the double smash, it then takes the usual 5 or 3 seconds before smashing again.

Dual Clubs
It now has two clubs, letting it smash Bloons to bits!

Price: $4,250 on Medium.

Appearance change: It now holds a second club.

Details: Now it smashes four times with 0.25 seconds between smashes. It alternates right-left-right-left. Again, it takes 5 or 3 seconds to attack again.

Spinning Attack
Tier 5 Upgrade: Has a 25% chance to spin for one second instead of doing a quadruple smash, shredding four layers from all Bloons in range. Spinning Ability: This Ability makes the Monkey spin around for 30 seconds straight!

Price: $15,500 on Medium.

Cooldown: 90sec.

Appearance change: The giant's visible size increases by 1.5x.

Trivia

 * This Monkey is a slight reference to the Gargantuar from the Plants vs. Zombies Series.
 * Almost all Towers would be OP when upgraded 5/5, but this...would be unbelievably OP.