There are several good kettles out there. Look for 18 gauge and preferably a sandwiched bottom.
Best low cost is a keggle (kettle made from a keg). There are lots of add-on parts made for them, they can be had relatively cheap and they can really take a beating too.
In my not so humble opinion you should avoid Blichmann kettles, thin, overpriced and weldless.
Did I just open a Pandora's box?
It boils down to budget and DIY abilities. MoreBeer sells excellent kettles if you have the money.