I see that most people have said the tip is the most important part of a cue, but I think it's the shaft. The best tip in the world can't do it's job on a shaft that's too stiff, too thin, too whippy, or has a terrible taper. A cheap tip will work on a good shaft with the right taper and feel for the player. You might like a certain tip over most other tips, but a good shaft will play well with a lot of different tips IMO.
James