I've also had very good experiences on airberlin and I try to use them instead of Lufthansa these days. I find the product, with the option of pre-ordering more substantial catering, quite good and consistent.
If you're talking about an airline which does not come up to oneworld standards, the it had to be Iberia Express, which I find myself on too often these days. Iberia mainline, too, to a certain extent, although I find them just about ok mist of the time.