What I recommend (also what I plan on getting) is the Yokohama AVS ES-100 in 205/50 or 55/16. The 50 will be a little smaller diameter than stock and the 55 will be a little larger than stock, it's up to you. There are so many choices it's unbelievable, what I would say is go to
www.b15sentra.net and search for "tires" and read for a couple hours. There is more information there than you would care to know. Your tire choice is really dependant on your budget and what you're looking for in a tire (cheap, expensive, summer, year-round, sticky, long tread life, etc)