One part tower defense, two parts dual stick shooter, and a dash of RPG; Bug Heroes is the most interesting blend of iPhone gaming I've see since Infinity Blade.
The premise of Bug Heroes is that you are a small, ragtag band of bug warriors who are trying to defend their food stash from the oncoming droves of enemy bugs. Your team consists of a machine-gun-toting ant, a beetle with a big stick, and a sword-slinging spider. Most of the game plays like a typical dual stick shooter, having you run around a map with a set size killing all that you see. The losing conditions are a bit different though. To lose in bug heroes, you can either have all of your characters die (you can hot-swap them throughout to prevent death) or have all the food stolen from your home base.
The trick of Bug Heroes is to correctly juggle your priorities. Keeping your units safe is obviously a big concern, but when they get hurt the only way to heal them is to eat food that you collect food throughout the map. Eating food drains your base food supply (remember, when you run out of food you lose) so it is important to do a good job splitting your time between food collection and base defense. All the while, you gain money per enemy kill that you can use to upgrade your weapons or the guns that guard your base, but killing units in droves involves your going out into the field, putting yourself in harms way.
Aside from the standard base defense "adventure" mode, you can also play in a "coliseum" mode that just pits you vs. wave after wave of enemies. With each mode spanning four levels, I can't recommend Bug Heroes enough due to its amazing replay value. If you enjoy dual stick shooters and have a soft spot for tower defense or RPG's, you'll absilutely love Bug Heroes.