Here's A use for Porygon.

When your opponent has a pesky psichic pokemon out, lets say kadabra,Right? 
How he beats all your basic pokemon before you can evolve them,right? Well, 
Send out Porygon,Okay. Then, no matter who goes first, porygon will get an 
attack turn. Next, attach a energy card to him and change his weakness to the 
type of pokemon who have most right now. Then, go kick Kadabra's @$$