You definitely want a cross-cut. It's the most secure!
It might be nice to get one that shreds credit cards and cds.
don't get a cheap one. How many sheets of paper will it shredd at once? does it do staples or paper clips or will it jam. criss cross shred is a must. credit card is a must
Cross cut or diamond cut is the way to go. Credit cards and cds shredding is a nice option too