Formula or Dimension.
These hubs are sold under a variety of brand names (IRO, Ben's, Harris Cyclery, etc.). They are no frills, reliable, durable, good looking hubs. Don't buy into the hype that more expensive hubs are more durable or faster, because the differences are negligible.
Hint: you can thread a freewheel onto a fg hub. Getting a fixed fixed hub gives you the most options...it could be double fixed, double free, or fixed-free.