I just finished field runners 2 and as the last level was closing down, all enemies vanquished, I was noticing the silence of the battlefield except for all those glowing gobs of green light that we're still pulsating across the field from the many plasma towers I had erected and it got me to thinking about some of the great towers in other games I've played and I was wondering what other towers other tower defense players would choose as their favorite. A close second to the plasma towers of both fieldrunners 1 & 2 is the hive tower in pixeljunk's monsters. I love all those bees hurling themselves at your enemies. So, what is your favorite tower in any tower defense game you've played? Doesn't matter what platform.
The most expensive one: once. The least expensive one: many, many times. It will be hard to play any TD game if you don't enjoy those two types in those amounts.