PicoLisp - 4 characters
$ pil
: ('0)
Segmentation fault
Body must be at least 30 characters; [I had] entered 28This is intended behaviour. As described on their website:
If some programming languages claim to be the "Swiss Army Knife of Programming", then PicoLisp may well be called the "Scalpel of Programming": Sharp, accurate, small and lightweight, but also dangerous in the hand of the inexperienced.