Since everyone says MSI, I'll say Gigabyte
Really, the brand isn't that important since they're all the same cards anyway. Of course, the MSI is overclocked, but others are too (possibly, that is). Just pick whatever you like.
I would say asus. Its direct cu II series are built like a tank and can be overclocked like crazy.
But msi has good service and it too has very good build quality.
^ thanks topgear for the info that a massive oc on hawx 1ghz wow! this card really runs cooler