Wigglytuff is also another one of those fun cards that revolve around a fun concept, but probably will not make an impact. 90 HP is good for a Stage 1, +20 Weakness to Fighting isn't helpful (Gallade and Lucario deal heavy damage to you and are widely played), no Resistance, and 1 Retreat Cost is cheap. Good Night Melody at a glace looks like an odd Poke-Power, as it puts both your active and the opponent's active to sleep. However, several strategies take advantage of this; for example, Xatu has a Poke-Power that allows it to shift status conditions to your opponent's Pokemon, leaving your active ready to attack. Balloon Attack does 40 for 2 Energy, but if Igglybuff is under it (ie, you evolved from Igglybuff into Jugglypuff into Wigglytuff), it deals an extra 20 damage. Igglybuff itself is a decent card to start with, so I can actually see this being used, though it's still annoying to have to evolve from a "Baby" Pokemon to get the bonus.
Modified - 5/10 (Fun combo to pull off at league or something, not going to see much action at States)
Limited - 8/10 (Poke-Power can be used to stall if desperate, and Wigglytuff is a decent Pokemon with decent attack costs)
Unlimited - 1/10 (No use here, not going to bring any memories of "Do the wave" Wigglytuff here)