I\'ve come across various solutions to this issue on the net.
Basically, I find having to hold down ctrl a bit cheesy, and I want the select list to just select what
Tony's answer makes the select arrows buggy, as they work only if you hold the mouse down.
I've combined a few solutions into this, and it works fine at least in Chrome and FF:
// multiple select: selectable without Control
$('select[multiple] option').on('mousedown', function(e) {
var $this = $(this),
that = this,
scroll = that.parentElement.scrollTop;
e.preventDefault();
$this.prop('selected', !$this.prop('selected'));
setTimeout(function() {
that.parentElement.scrollTop = scroll;
}, 0);
return false;
});