Make the job of corking your wine easier.  Since wine corks are uniform in diameter a corker helps to compress the cork so that it will seat into the wine bottle; it will then expand slightly to fill the opening.  Without a corker the chances of breaking bottles increases substantially as the cork is the same diameter as the bottle opening.
Plunger corker
Price: $10.95
Portuguese double lever corker
Price: $24.95
Portuguese floor corker
Price: $72.50