OK,  I just thought of this combo last week, and if it sounds too good to be true, it just might be (I'll explain later).
 
===================
Scizor            80 HP    M
===================
[M] False Swipe (?) Does
damage equal to half the
defending Pokémon's
remaining HP (rounded
down to the nearest 10).
 
*[3] Double Claw (20x) Flip
2 coins. This attack does
20 damage times the
number of heads.
 
Weakness: F
Resistance: Grass
Retreat Cost: 2
===================
 
*I believe Double Claw was mistranslated. The US card has "20+" instead of "20x," which implies that the attack SHOULD read:
 
Flip 2 coins. This attack does 20 damage plus 20 damage times the number of heads.
 
However, I believe Wizards' official ruling is that the "20+" is the misprint, not the attack description, so I went with this one. (You don't need that attack for the combo anyway.)
 
===================
Porygon         40 HP    C
===================
 
[1] Conversion I (): If the
Defending Pokémon has
a weakness, change its
weakness to any type
other than colorless.
 
[3] Psybeam (20): Flip a
coin. If heads, the
Defending Pokémon is
now confused.
 
Weakness: F
Resistance: P
Retreat Cost: 0
===================
 
Alright, those are the cards, here's the combo (in case you haven't already figured it out). Use Porygon's Conversion to change the Defending Pokémon's weakness to Metal, then use Scizor's False Swipe for an instant KO!
 
False Swipe damage = [(Defending Pkmn's HP) / 2] * 2 (for weakness) = Defending Pkmn's HP
 
It won't work on Pokémon with an odd number of HP, since False Swipe rounds down, but a Plus Power easily remedies this. This also works with Base Set Porygon, but TR Porygon is WAY better (10 more HP and free retreat). Also, this will not work on Pokémon with no weakness. Babies, Darkness, and legendary birds (just to name a few) are immune to Porygon's Conversion I. So, it's a good idea to have other Pokémon to support this combo.
 
This strategy is mainly useful for those pesky Pokémon that just won't die...er, faint (Chansey, Steelix, Charizard, other 120 HPs). Of course Metal Energies on the opponent really put a damper on this, but Plus Powers and ERs work in a pinch. Since no Pokémon have resistance to Metal, you don't have to worry about that, but you DO need to worry about Unown M. Gust and use another hard hitter (like MP Mewtwo or Rocket's Scyther) to KO that pesky Unown fast.
 
OK, I think I've gone on long enough. As you can see, this combo has its flaws, but it does have potential. Let me know if you like it or have any suggestions. No spam/flaming please.
 
BTW, this is my first submission to Pojo.com, so don't judge me too harshly! o^_^o Oh, and is it alright if I plug my Pokémon Apprentice theme? Oops, did I type that? *psst! email me if you want it! it's really good!*
 
Ankh-Morporkian
AnkhMorporkian@flashmail.com