If you had something like a mascot-character you could use his/her name. Otherwise, if the enemies are unique and fun you can name your game after them. For example, if your enemies are snails, you could go something like:

Snail's Trail

Snails Hate Towers

Snail Squasher

...etc...

Or using the mascot character:
<Mascot's name> Hates Snails

<Mascot's name>'s Towers

<Mascot's name>'s Treasure

Otherwise go for one of the jewel options that were given in the posts before. ^.^