Mamiya 6 or 7 if you want interchangeable lenses and a very small kit. I love my Hasselblad too, but it's bulkier and requires a tripod more often.
Agfa Super Issolette (or Ansco Super Speedex is the same) if you can live with a single normal lens. These fold up nice and small and take excellent pictures with a look that is more classic than modern.
Super Isolette is very good but I find that I need kind of lock that prevents the release of the folding plate.
OM-1n: Do I need to own a Leica?
Rolleicord Va: Humble.
Holga 120GFN: Amazingly simple yet it produces outstanding negatives to print.