I probably use the plugin 'tComment' more than any other plugin. It toggles code comments, based on filetype. I often try to toggle comments by hitting 'gc' on machines that don't have that ability. Very simple, but has quickly become indispensable.
I keep a list of links to things related to Vim, and the list of plugins I use is at the very bottom, if you're interested: http://mileszs.github.com/
"Without snippets you’d have to type this out every time"
Well, no. You'd write your own function to insert that text and map it to some key sequence.
Now, snipmate may make the addition and maintenance of such helper functions much nicer, but if people are really typing the same stuff over and over they're missing out on a key value of a programmable editor, not just lacking a plugin.
http://code.google.com/p/yasnippet/