YMMV: Bubble Tanks
- Demonic Spiders: Heavy Killers. Like their name suggests, they're very fast and are equipped with machine guns that screw up large characters. Also they'll always be in at least pairs.
- Game Breaker: With the "improved sell-back" and "cheaper Ghost Towers" upgrades in Tower Defence 2, you can actually profit by building and selling tier one ghost towers. Admittedly it takes ten iterations to afford a single basic tower, but since the game won't start until you let it, with a lot of patience and mashing the 2 and S hotkeys, you can garner a substantial early advantage.
- The Mega-Tower, which can be made by morphing 4 fully upgraded towers into one, allowing for vast amounts of attack combinations. Even worse is the MegaMega-Tower, which is ''4 mega-towers rolled into one. Next thing we know, the 3rd game will allow us to morph 4 MegaMega-Towers into one MegaMegaMega-Tower...