Fixies were cool about 10 years ago when they were still a novelty among cyclists. They've blown up in the last 4 years and the trend is pretty much over. If you want to be trendy, get a BMX. They'll be really popular in 2-3 years.
If you want a practical mode of transportation, try to find an old 10 speed at a garage sale. I found a vintage Raleigh Gran Sport in my parents' basement that I've been riding for the past 3 years and love it. I replaced the drop bars with flats and upgraded the tires and it's easily the best bike I've ever had. It's fast, efficient, smooth, and looks great without being too flashy (aka a good candidate for bike theft).