In Europe: Barcelona, San Sebastian & Vienna (still have to make my way to Lisbon & Stockholm)
Been to those three cities many, many times and still enjoy going there. Just so much great architecture and interesting stuff to do, plus good food (great in case of San Sebastian) and good nightlife (next trip to Vienna & Barcelona will be in May, while I wait for my new visa)
In the US: San Francisco (close 2nd NYC)
Other than that:
Maldives for a island getaway/honeymoon type trip, CR (pacific coast) for a beach/surf vacation and if I wasn't living here, Brazil would be high on my list for sure.