Weapon Enhancer Bloon can be used to boost friendly Monkeys, particularly many low-cost Monkeys such as Barrel of Monkeys or high-ammo Monkeys such as Frag Bomb Shooter. It also can stop certain attacking Monkeys from getting taken by Bed Time (notably Jungle's Bounty Druid).
If these Bloons are not popped, they can be used to counter aggro, though these Bloons are still vulnerable to board clears such as Spike Storm! and Gwen's Firestorm. Notably, they can easily be one-shot by Super Monkey Storm.