GTA: Ant Buster
You and your friends are having a party at the great outdoors. They told you to go hiking with them, but you know that without someone to attend to the picnic basket, party ants would grab all the food and you just can't let that happen. But, your friends are persistent, so you just let some mini gun to to fight the ants. The ants will keep on coming and you need to stop them. You can erect some towers to fight them with. Each kill would earn you money and you can use the money to upgrade or buy another tower.