most towers can unlock an ability, in order to achive you must upgrade the right row completely and have unlocked your rank required to achive high power. You then activate the ability's yourself Here are some of those ability's:

absaloute zero

blade maelstrom

call to arms

glue striker

ground zero

moab asassin

moab takedown

sabotage supply lines

summon pheonix

super monkey fan club

supply drop

turbo charge