More like what can't you do with a fast CPU. Anything you decide to do (gaming, fooling around on the internet, work..) wil be done faster over a slower CPU. Like Scottie said:
"IF you have a Hyundai, you can get anywhere, but if you have a Ferrari, you can get there faster, no matter where you are going.
So no matter what program you are using, it is going to work faster with a faster CPU, Internet Explorer, Word, Excel, Photoshop, whatever you use..."'
.