+1 on the chesters, I run the gamut podiums for a wider platform and more pronounced pins but I'm really thinking about the deity T macs... the chesters are great bang for your buck Price range?
There is another post about flats, some good feedback in there.
I was looking for flats as well, the vast majority of people said the DMR Vaults are the pedal of choice but the RF Atlas, Hope F20's and the Diety TMAC were also mentioned as good pedals. I went with the TMAC as I got a great deal from a buddy at my LBS. They have almost perfect pin placement and one of the biggest platforms, so if you have big feet that may be your best bet. My 510's do not move on the pedal so if you like to change foot position the TMAC will annoy you.
You really cant go wrong with so many great options but my only advice is buy the best quality pedal you can afford. If you cheap out you will regret it.
Currently running some Bontager Line Pros, price was kinda high and they are a bit thick but seem like a good pedal. My LBS has limited stock and I needed something to replace the clipless XTRs that came on the bike. I paired them with some DC high tops for now until I find a proper high top that fits my ankle brace.
DMR Vaults FTW! Been on them for almost 3 years now and would not even consider another pedal. The grip and feel are amazing. I wear Adidas Shell Toes (Classics) to ride in instead of FiveTen shoes though. I do not like any of the FiveTen shoes at all.
Now, my daughter uses Deity BladeRunners and loves them. And she wears FiveTen shoes for both her flats and Time clip pedals (she has 2 different pair). I have tried to ride her bike on occasion and I do not like the feel of the BladeRunners. The are a completely flat pedal and to me they are just uncomfortable. My Vaults are concave and feel great even after long epic rides.