Non-TCG Cards
A quick explanation before the goods - the first two playing cards I came across for Mewtwo, when I started hunting for anything and everything with the psychic powerhouse on it, were an Ace and a King. Those two cards together form a blackjack, and were the basis of the idea for the above header. (Blackjack rule snobs will be happy to know I specifically asked for the wording to be for an S17 table.)
Anyway, onto the card collection!
Mewtwo Strikes Back 3D cards

Granted these don't have Mewtwo on them, but they are from the first movie. Good enough to be included.
Uncut Burger King card sheet

There are individual Pokemon cards for all of the first 151 on a set of 20 different uncut sheets I have - rather than photographing all of them, I took one picture that'd let you see all 9 of the scene cards on the back...
Mewtwo BK single card

...plus the Mewtwo card itself.
Misc. Japanese Mewtwo card

I have no idea where this came from.
Meiji card

Another one I have no clue where it came from - I think it came in a bulk lot, as it definitely wasn't in the best of shape when it arrived.
Carddass Mewtwo

These things seem to be uncommon but sell well when they're offered. Most of the good quality ones are in the $20 range.
Mewtwo Ace of Spades

It's only fitting that Mewtwo's put on the most powerful card in the deck.
Mewtwo King of Diamonds

The first of the two playing cards of Mewtwo that I came across. And with the header art done above, you see a proper show of what happens when a King meets an Ace.
Tiny 9 of hearts

Would really like to see someone try and play cards with a deck this small!
Topps Promo Card Set

...yeah, I'm sorry, I wasn't taking 82 individual photos of front and back of all of these. I have the full set and figured this would be the easiest way to show it in the smallest amount of pictures that are still of decent quality.
Burger King Gold Cards

I really should have thrown these in dupes but (A) these aren't all that impressive and (B) taking a photo of a single one of these never did well, flash or not.
MechaMew2 Card

Probably the most impressive thing in this section - this little beauty came from the Pokemon Live! stage show.
Apparently this is a difficult find as it's been popping up on eBay lately at inflated prices.
...admittedly it would be nice to someday acquire MechaMew2 himself. That's a bit of a pipe dream right now though.
Apparently this is a difficult find as it's been popping up on eBay lately at inflated prices.
...admittedly it would be nice to someday acquire MechaMew2 himself. That's a bit of a pipe dream right now though.