I love me a good flea market, junk shop, garage sale, any place you can get cool old things for very cheap. Paris has its share of great brocantes and vide greniers, but the best Paris flea market I've been to is at Porte de Vanves.
Along this strip of vintage wares, any antique or retro lover will die of happiness at the sight of stand after stand overflowing with vintage postcards, clothes, jewelry, books, posters, cameras, paintings, dishes, etc. etc. etc.
I prefer Vanves because it has a super relaxed vibe, authentic and friendly vendors, and most importantly, there's no maze of crappy new stuff and designer knockoffs to get lost in (as you'd find at Puces de Saint-Ouen). It's only open on the weekends, and supposedly only until 2pm, but anyway, the earlier you get there the better, for higher-quality cherry-picking.
I loved these teacups made back in the day for Victorian men who didn't want their mustaches to get wet. It would be the perfect gift for the dandy hipster in your life. Alternately, you could use the little corner to hold your tea bag after you've steeped. At the time, I thought, "Surely, Jenna, you cannot buy these delicate teacups; you'll never get them home intact." But I was crazy for them, and have been thinking of them ever since, so my advice is that if you really love something and it's affordable, buy it and figure out how to get it home later.
Trolling these collections always brings me a vague sense of melancholy, because you can see that they belonged to and were beloved by someone many years ago. They're relics of another era, a different world which no longer exists.
On my trip to the Vanves flea market I felt overwhelmed by so many things I wanted. I thought I was going crazy shopping, but in the end I spent less than 10€. I got this beautiful, autumnal magazine cover from the 1920s for just 2€ (and isn't it so Lady Mary?):
I came across a stand that had stacks and stacks of magazines from the 1800s through the 1950s for just 1€ apiece, and snapped up a few to frame the covers and use the inside art and typography to make some homemade stationery:
I fell hard for this gorgeous old red book, just 5€. I think it'll make a fabulous hollow book (DIY instructions here).
And I really couldn't resist a little vintage pin (50 centimes), proclaiming my inevitable "crazy success":
Marché Aux Puces de Vanves Flea Market
Every Saturday-Sunday, 7am-2pm
Métro: M13 to Porte de Vanves