Pi (Aronofsky) - happens to be a really messed up film too...
Plenty of French films, including:
L.627 (Tavernier) - still one of my favourite cop films
36 Quai des Orfèvres (Marchal) - another good one about 'les flics'
Faubourg 36 (Barratier) - from last year, a really nice feel-good film celebrating the 1930s French music hall and anti-fascism...