Park Tool Chainring Nut Wrench - CNW-2C $3.95
The wrong tool is always a bad idea.
One of the quickest, easiest ways to destroy a set of chainring nuts is to try jamming a flathead in the slot to hold them in place. Do yourself a huge favor and pick up the Park Tool CNW-2C Chainring Nut Wrench. You'll be glad you did when you get your rings off without a hacksaw and a shredded crankarm spider.