I'm probably risking life and limb by suggesting to DIS that this film is little known, but my nomination would be 'The Young Poisoners Handbook'..
I was rather hoping that there'd be the whole film on Youtube (especially as the auto fill search title 'The young poisoners handbook 'full movie' came up??!) but alas not.....here's the trailer anyway.
Another would be The Billy the Kid and the Green Baize Vampire:
Apologies in advance for telling you about some films that you already know about!
Any other decent recommendations, post them below me hearties!