Probably Carcasonne - the Hunters and Gatherers variant - simple, pretty and tactical enough for advanced play. Not good for the pub though.
But I also love Polarity which we play in the pub in teams. This is great fun because it has tactile weirdness and dexterity factors as well as tactics and gets very tense with magnets wobbling and threatening to fall all over the place.
We play this other trading/resource card game called Beananza which also works well in the pub. As does Loot and Pig.
I would like Perudo for it's mathametical vs bluffing tactics but I'm doomed to lose on both counts!
For something quite different try to borrow Pandemic, because its a co-operative game against the system. You may not like it; I'm still getting into it.
Two games I expected to love but strangely don't are Catan and Power Grid. You just can't tell until you try.