Well over a decade ago, I spent an afternoon in a stationery store trying out as many pens as I could. I fell in love with the Pentel EnerGel NV 0.5mm (smooth, dark, consistent, feels nice in the hand) and haven't looked back since. I'm glad to see that this website has a high opinion of it too.
Somebody in a previous HN threat recommended the Pentel EnerGel .7mm pens and I picked some up at WalMart. Best pens I've ever used and they're like $1.50 each.