Wandering along the streets of Budapest may bring you to some unexpected places and surprise you with the variety of weird things you can buy. Flea markets and thrift shopping are a prominent part of local Hungarian culture. If you don't like second-hand clothes, you may still find some great vintage souvenirs.
Some popular shops may be hidden from tourists in backyards, and you may need a local person to show them to you, but you will never miss the biggest flea market PecSa located in the middle of City Park. Usually, there is a symbolic 1-Euro entrance fee, but on special occasions, the ticket may cost more. This market is open only on weekends from 8 a.m. till 2 p.m.
If you have a desire to do some "flea" shopping on a working day, then head to Ecseri market on Nagykőrösi street open daily. But keep in mind that new arrivals come there on Saturday morning. Also hunting for good antique stuff can be joined with some sightseeing along Danube Promenade, where every Saturday vendors line up on Újpesti Piac-Placc market.