The Bouncer
Costs 2000 coins (it is reasonable based on what it does.)
An overview:
It launches enemies into the air, causing fall damage.
This is a special tower, as the greater number of towers in an area, the height they reach would stack. Either this or it can go to the highest point the best tier in the area goes to. For example, a tier 2 Bouncer and a tier 3 Bouncer are in range of mobs. Either they would go to the height of the 2 and 3 tower put together, or it would just cancel out and go to the tier 3 tower's height. The Bouncer would fit perfectly with the Levitation effect.
Note: this obviously does not affect flying mobs, but it can affect cave spiders.
Tier 1:
It costs the 2000 to buy, has a range of 13 and lifts mobs up 8 blocks, dealing the equivalent of 2.5 hearts of damage.
Tier 2:
Costs 1500 to upgrade to it, has the same range and lifts mobs up 10 blocks, dealing 3.5 hearts of damage.
Tier 3:
Costs 2250 to upgrade, and lifts mobs up 12 blocks, dealing 4 hearts of damage.
Finally, Tier 4:
It costs 3000 coins to upgrade to this final tier, and it lifts mobs up a massive 13 blocks, dealing 5 hearts of damage.
Now that I go over this again, I can imagine how having stacked block lifts would be slightly overpowered. Maybe just the highest tier can do damage? Still, thanks for (hopefully) looking at this.