the fastest would probelly be the one that comes with X, very basic and does nothing that most people need for it to be useful but you did ask for speed
with a program or two in the backgroud its usable, it depends on your needs
i like the rat posin idea, so much so that i use somthing simmilar full time (wmii). on a Z these are great as you can get the benifits of X without touching the screen alot, it does however help if the programs you are uisng have good keyboard support
firefox has a great extension that allows you to hit a button and have numbers and letters come up next to every link, you then type the number of the link you want to follow. its called somthing like hit-a-link or hit-a-hint
never use the touch screen again (says someone who just uses the terminal and screen )