Why am I doing this? To be completely honest, I'm not sure but personally, my own deck only uses grass energies and two dark energies (since weavile pulls them out) and I have in total SIX different types - my strategy is to have lots of types to target different weaknesses. So maybe it's to form strategies or maybe I'm way off. Anyway, here's the updated list:
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DP: (none).
MT: Abomasnow, Tyranitar, Whiscash. Barboach, Snover.
SW: Weavile, Sharpedo, Breloom, Gallade, Salamance.
GE: Marshtomp, Houndoom, Latias, Latios, Slowbro.
MD: Burmy.
LA: Regigigas, Rayquaza, Froslass, Starmie, Poliwrath, Mamoswine, Piloswine, Swinub, Probopass, Lanturn, Vileplume.
SF: Infernape, Empoleon, Torterra, Salamance, Mamoswine, Magnezone, Magneton, Magnemite, Swinub.
PL: Dustox, Houndoom, Cacturne.
RR: Lucario, Houndoom, Froslass, Drapion, Rotom, Pikachu.
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Is that everything? No doubt it will be quite hard to find some more, its a bit of a challenge now. [*EDIT 7:52PM]