A sloughful of exceptions to "no exceptions" Brazil visa:
(provided by very knowlegeable source on another forum)

"Exceptions like Letham are rare but not uncommon:
You could travel to Leticia in Colombia, the border is smack in the middle of town, the same town is called Tabatinga. It has an airport, but is not major. The other option would be the Peruvian town of Inapari, they actually have a bridge (so it's better than Letham). The border control is actually beyond the Brazilian town of Seringal Paraguaçu. I just wonder what on earth you'd want to do there, being in the middle of nowhere and all. The town of Cobija in Colombia is also divided in the middle by the border, so no border control. On the Brazilian side it's called Brasileia. The airport is on the Bolivian side, so it suits your needs. You could also cross by boat from Guayaramerim in Bolivia to Guajará-Mirim in Brazil. Part of the Bolivian city of Puerto Quijarro is in Brazil. It's near Corumbá, bit there is a border control. Another boat option would be from Puerta Carmelo Peralta in Paraguay to the Town of Tres Barras in Brazil. Bela Vista, Paraguay, is also divided by a border, but the border control is in the middle of town. Another great place to visit is of course Ponta Porã. The Brazil Paraguay border divides the town in two in the city center. The town of Aral Moreira is also divided by the border. Of course, Parguay and Bolivia require a Visa for Americans, so that would be an obstacle to overcome. Maybe there are similar towns between the Colombia - Boliva border and Bolivia - Paraguay border. That way you could use the Bolivia an Paraguay options. The town of San Antonio in Argentina (Santo Antonio do Sudeste in Brazil) is also divided by the border, as is Bernardo de Irigoyen/Barracão. There is also the city of Santana do Livramento between Uruguay and Brazil that is divided by the order. As is the town of Acegua and the town of Chuy."