Shell is one of them, but I do not think that they are marketing that angle properly. Have you ever seen any real info on the pumps that properly explain what Top Teir is and it real benifits at the gas pump?
Once I heard about it on the Net I started buying more Shell gas then the other brands, but I sure did not hear about it from Shell.
Where I grew up we had an Esso and an off-brand. The off-brand had water condensation problems with their storage tanks so I always used the Esso. This was obviously before the whole Top Tier thing started.
I've since moved away from there but I've always had it stuck in my head that Esso was the 'good' gas station. Whenever I move I habitually learn where all the Esso stations are and only use them unless I have no choice or there's a significant price war.