Sums in lane (Exh, flash, TP, etc.)

The more I play, the more I realize that with certain play styles and champions that you don't have to take the normal flash+(whatever) for your lane. I see Trynd's take Ghost a lot on top lane with ignite. Now, as a noob, I'm not sure what ghost does, but it is quite popular when I duo with my higher elo friends. I've recently started taking TP and Ignite when I top with Swain. It works wonders. Hell, ignite on Swain is just the icing on the cake with his other abilities.

**Anyway, I kind of **got off track. Obviously, flash is useful, but it's not always needed, yea? What positions do you run and what sums do you generally take? Does it work? What are some pointers to be given to those who can capitalize off of other sums?