There are a few pokémon that require different types of energy for their
attacks (not counting colorless!)  You think "well that sucks!"  But they
deserve a second look!

Exeggcute; a Grass type with psychic-energy attacks:
  It needs a psychic to put the enemy to sleep.  It can stall while you're
waiting for Exeggutor, but can't do damage.  You have to add two leaf energy
to use Leech Seed, but when it evolves both attacks only need *ONE* energy
card.  It's utterly pointless to plop both types of energy on Exeggcute!  So
basically, Exeggcute can be used in two ways without energy waste. 
Use #1:  Several in a grassy deck without Exeggutor.  Leeching life from an
enemy to heal yourself is an excellent thing to do! 
Use #2:  A few in an all/part/mostly psychic deck, with Exeggutor.  You plop
one psychic energy on Exeggcute, put the enemy to sleep.  Sure, it might not
stay asleep but it's a stall.  Then if you're lucky you can evolve it and
thus the energy requirement of one colorless energy is filled for Big
Eggsplosion.

Psyduck & Golduck; Water types with psychic energy attacks:
  These are excellent bi-color pokémon!  Psyduck needs a psychic energy for
one attack, and a water for its other ((damage-dealing!!)) attack.  If you've
time, plop BOTH types on, and when it evolves to Golduck it also needs one
psychic energy, but lo and behold its other attack needs two water *AND ONE
COLORLESS* (hmm, recall that lonely psychic energy)  I think The
Psyduck-Golduck combo is considerably better than Exeggcute and Exeggutor!
(personal opinion, I don't like eggs, yuck!)  Not only do the energy
requirements work out "swimmingly," Golduck is an energy remover (for one
energy card less than Dragonair and same amount of damage)
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