I really like the '01 masks and thus decided about a year ago to finally collect them. This is what I had in January 2016:
Some of these masks were taken from the sets.
This is my collection now:
Nothing taken from any sets - I wonder if I should get another infected Hau, too?
So, these are actually the only rare masks i care about. Ok, except that I would really like to have '08 Takanuva's mask, Toa Lesovikk's Faxon, the Great Ruru in dark blue and the golden Ignika... They're so hard to find for a reasonable price (or at all), though...