Beyond your list, and deployment, there are other ways to demorolize your opponent during the game. One of my favorites, is being able to take down a transport, and then wiping out the entire unit that was inside with the next shot. Example... Hydra squadron blows up the rhino, Basilisk or artillery battery kills everything that came out. Another example might be, Assault terminators assaulting multiple units or tanks and destroying or breaking it all. Having a hammer in your list, really can bring home the victory in one fell swoop.
Coming up with your hammer is part of what makes list building fun. Seeing it in action is part of what makes playing fun.