The Firebat is the second unit available to the Terrans, but its role is limited. It can be effective on a cluster of targets all bunched up together since their attack will damage all units in front of them instead of one, but only on light armored units. Most players dont use the Firebat because of its limited usability and it is the only Terran unit that has to get close to the enemy to attack.

Having a few Firebats with an Infantry squad is a good thing especially against Zealot groups which tend to pummel Marines. Just don't go crazy building them, they are designed to keep Zealot and Zergling groups at bay, nothing more. Plus with their relatively low health, they still die fairly fast even against their proper targets.

One tactic that is used with Firebats is a surprise resource attack. This is done by filling a Dropship with a few Firebats and taking them to their resource workers and unloading them. Since workers tend to be closely packed together, the Firebats splash attacks will make short work of them.