Often you have to set the filetype manually, for instance, when you paste in the contents to a buffer without a filename.

These are filetypes that I personally use often:

description Vim filetype third-party syntax file name included in my dotfiles
iCal icalendar [1] icalendar
perl perl
JSON javascript
markdown markdown [1] [2] mkd

description	Vim filetype	third-party syntax file	name included in my dotfiles
iCal	icalendar	[1]	icalendar
perl	perl
JSON	javascript
markdown	markdown	[1] [2]	mkd