Absalom is the most common by far I would say. However if you really want one that isn't Absalom there are a few choices.
Katapesh -South of most civilized lands, sprawling across a valley of blazing-hot sand, is one of the most incredible and wondrous cities in all of Golarion: the great desert metropolis of Katapesh
Kaer Maga -Standing atop the Storval Rise, the cliff-top city of Kaer Maga is built inside the ruins of an ancient fortress: a six-sided ring of 80-foot-high seamless stone, stretching more than a half mile in diameter and topped with towers of every shape and design. Also known as the Asylum Stone, Kaer Maga has served as a refuge for exiles, misfits, and ne'er-do-wells fleeing persecution and prosecution for thousands of years, and is known throughout Golarion as a place where anyone can fit in, and where anything can be bought and sold.
Magnimar- stands as one of the two major city-states of southern Varisia. Founded by Korvosan dissenters in 4608 AR, the City of Monuments now stands as a rival to Korvosa in an open war of coin and words.
Korvosa -the largest city found in the wilderness area known as Varisia, and serves as the seat of one of three city-states that claim independent authority over their individual holdings in the region. Though its citizens and traditions have strong ties to the nation of Cheliax, with many of its people tracing their ancestry directly to servants of the Empire, the city's location at the mouth of the Jeggare River and the presence of a highly-defensible harbor have contributed to the establishment of Korvosa as a primary hub for trade; various cultures and peoples can be found within the city's walls as goods move in and out of its gates.
There are likely others, but if you want your bond to be used most often Absalom is your best bet. However if you want a something to build a story around, that will come up at some point the above choices are excellent ones.
As a personal choice I like story. My Half-orc Cleric knows Kelish based on that his human parent is Kelshite. Has he ever used it? No, but it's never hurt him either.
