I don’t have too many rare masks, but I’ll try to remember as many as I can!
Mask of Creation (If that counts)
'08 Avohkii
Glittery Avohkii
Trans-red 2015 Hau
Gold Krakahn
Lhikan’s Hau
Movie Krakahn
Trans-Lime Green Miru
My brother has
Chrome Hau
Gold Avohkii
Wow… Maybe I have more than I thought! 
Glitter Avohkii
Dark Grey Hau
Some uncommon nobles (if that counts)
SDCC Skull Scorpio mask (Sealed)
Mask of Creation
Mask of Control
Gold/copper Pakari
Silver Akaku
The Krana is gunmetal, and the orange on the krata is metallic…
The Brain slug is a joke.
Also, thanks for posting this… otherwise I would have never known I had three glittery avohkiis… I swear I only ever got two… wtf? I am now compelled to make a moc from them… but I don’t know what…
None of those are really…rare, they are all from mainline sets.
SO MUCH TRANS GREEN
It almost looks radioactive
IT LOOKS AMAZING.
#Trans-green4lyfe.
I’ve got an orange Vahi, if those are rare. I guess it’s at least sought-after since it is the only G1 mask that has appeared in G2…
Oh, and the Golden Skull Mask. My wallet was not ready. :’(
Throws handfuls of cash in direction of Russia
…
Wait, is the Mata-Red Ruru rare? It came with the BIONICLE clock, and I completely forgot I had it. Looking at Bricklink, I can’t find any actual set that included it in that colour…
I don’t remember ever seeing it anywhere so yeah,probably.
The Mata red Ruru is a misprint mask. Not incredibly rare, but still rather sought after.
I have a light bronze-ish colored Kakama (Mata version).
Not sure how rare it is, but eh. I like it.
Not all of them are misprints, some came with the clock. So it is the most common of the mata colored turaga masks I belive
Not as common as the black Ruru. 
y’know, it being on Hafu ‘n’ all.
I can finally say, “I’am the proud owner of a chrome rua”
Chrome Rua owners unite!
Two chrome Rua’s to be exact…
I also had two chrome ruas but I gave one to my friend.
How could you do such a thing?
I did not need it, and he wanted a Rua, but it would cost him more than he could afford… so it was a win-win situation
So what did you get?
