How on earth is it useful?

[vanderbilt_grad]

To expand on the good posts above, it might help to read this:

http://www.pojo.com/CardofTheDay/2008/8-22.shtml

That's a link to Jason Klacynski's world report. Top 4 is where the Jolteon* really did it's magic.

 

[yoyofsho16]

I was there and watched that game... it was amazing. The best game I have ever witnessed in all of my 9 years playing the game. It is searchable, that is why it is better than Plus Power.

Jason had a Gardevoir with I think 2 Psychic energies and a Call Energy. He advanced it, played Lake Boundary, and dropped Jolteon* to OHKO Gallade to win it.

 

[PokePop]

Yep.
Final play of the game.

Of course, Crobat G is a much superior card for this purpose, but it was not available at the time.