The Yomato gun is a valuable upgrade for your cruisers. Although it takes a long time to recharge - it does give you a few powerful blasts when you need it. The Terran Defense Terrans have the strongest defense of all the races. Bunkers are formidablethroughout the game and can stop numerous invasion attempts. Missle turrents provide powerful anti-air defense as well as detection.
Siege tanks provide extremely powerful ground fire on advancing forces.
The three when used together are nearly unbreachable. To setup a great defense you need to consider your opponents. If you are playing protoss or zerg you will want to have at least 1 firebat in each bunker. However if your playing terrans you will only want firebats in your bunker if your enemy is using firebats against you. If your opponent is protoss and they are using a ton of zealots against you, you may want to put 2 firebats in a bunker.