you may only make one free action attack per turn, you may make any number of no action attacks on your turn.
if your stunned, unconscious or dominated you cant take free actions. but you can always take no actions
Ah, yes, I had forgotten they added that "only one free action attack" clause in the wording for Essentials. Free actions have always had a 'DM discretion' clause which I assume was always intended to provide an explicit 'out' to the DM so they could put the kibosh to things like endless cycles of free attacks (which have arisen a couple of times with various combos). That kind of stuff got errated pretty quickly, but I guess now it is REALLY truly and explicitly illegal. Truthfully there are very few 'no action' attacks, and the ones that do exist are at least notionally coming from something outside of the character itself.