I would love to meet new people and not just see a city, but have conversations and staying with the people who live there. I think that way you get a way better idea of the culture and a much more interesting experience than just staying in a hotel, hostel, etc.

I loved the Iguazu falls, cycling at night through Buenos Aires, tasting (a lot) of wine in Tarija, stripping for 600 Bolivian women in Sucre, going to a crazy concert in Medellin, learning Salsa in Cali, climbing the pichincha mountain in Quito and so many things more!