Can't go wrong with Mamie Clafoutis.
Things to eat:
Croissant
Pain au chocolat (they call it "chocolatine" here)
P'tit cheddar (it's a cheddar version of the pain au chocolat)
Caneles
Mini tarts (apricot rocks)
What to avoid
Their savoury dishes. I've tried their pies to their tarts in smoked salmon, and they're all terrible. If you want something savoury, take the soup.
All that said, if you go before 8 a.m., you'll get better pastries otherwise they'll give you the ones in the cases that are all doughy, old and bready.
I've been burned before... that's how I know.