Promo Mew, or perhaps more properly, Fossil Mew, is actually pretty decent.
        Here are some of its stats, if you still haven't gotten one:

----->50 HP

(Not great compared to some of the "Mighty Stallers" but Mew is NOT a
staller!)

Attack #1:  ----->Psywave for one Psy energy.  Does 10x the number of energy
cards on the defending pokemon.

(that x kills it... can't do damage if there is no energy... so you take Mew
out against a fully pumped Tangela... then the opponent's Venusaur draws away
all of its energy and you're effectively immobilized!  Sure, it can do what,
40-50-60 damage to a "fully pumped" Charizard... then Charizard goes and
blows Mew away.  Poor Mew.  Burnt card.  Very sad.)

Attack #2:  ----->Devolution Beam for 2 Psy energy:  Choose an evolved
Pokemon (your own or your opponent's).  Return the highest Stage evolution
card on that pokemon to it's player's hand.

    (That's the point where most people stop reading.  But let's finish it
up!)

That Pokemon is no longer Asleep, Confused, Paralyzed, Poisoned, or anything
else that might be the result of an attack (just as if you had evolved it).

    This is Mew at its greatest!  Remember that Ditto dilema... retreat it
with too much damage and it's dead?  De-evolve an Ivysaur with 40 damage and
it's dead too.  De-evolving can destroy already-damaged pokemon!  But it's
not just that!  You can de-evolve your OWN pokemon too!  Evolved that
Aerodactyl too soon?  Did they remove too much energy from your Pidgeotto? 
They haven't found a way to *force* someone to evolve yet!  Okay, so benched
pokemon can't be asleep, confused, paralyzed, poisoned, etc. and de-evolving
the opponent's active to cancel a status change does seem kind of annoying. 
All of that trouble to poison their Blastoise and then when you de-evolve it,
whammy there goes that poison!  I'm trying to think of an advantage this
would give you, the Mew user... but I can't think of one.  How about to
counter Evil Primeape's pokemon power... PP when it's confused its attack
does extra damage.  Its attack causes it to become confused.  Maybe it's
meant to counter pokemon powers in general.  If they fail to re-evolve their
de-evolved pokemon you could always try an Impostor Oak on them.  Sure, it
kills the trainer Pokemon Breeder, (raspberry at all those people who leave
Wartortles, Ivysaurs or Charmeleons out of their decks!) but other than that
I think Mew is just the standard non-evolving card, not too great, not too
lousy, just "decent."  And it's kinda cute
too... if only it wasn't pink!

Retreat:  1 colorless (have you ever seen a retreat cost that was NOT
colorless??)
Weakness: Psy (duh)
Resistance:  Zilch

It's about 16 inches high and at 9 pounds it weighs more than the 5'11"
Dratini!

    Rainy, the Furry Blue Mock-Dragon
        (who now has "Blue Mew" to the tune of "Blue Moon" stuck in her head)