Sams Teach Yourself Game Programming in 24 Hours

Are there any games that wouldn't require keyboard support?

Sure. Any game that requires extensive point-and-click style input, such as a card game, would probably be fine without any keyboard support. In fact, you create a memory game in Hour 8, "Example Game: Brainiac," that is perfectly suited for mouse input alone. However, if you can figure out a way to add keyboard controls to mouse-centric games, by all means go for it.

Is it possible to mix keyboard and mouse controls?

Of course! This actually hits on an interesting point not directly covered in this hour: Many games work great by combining mouse and keyboard controls together. A good example is the strafing feature in Doom, which also works with the mouse; it is activated by holding down the Shift key while moving the mouse left or right.