gastrodon is a great counter to rain and overall very hard to take down. it likes surf-spam partners, Heatran, Volcarona, chandelure and any other Pokemon that it can form a fwg core with. Most use either rindo or sitrus berry. Rotom-W counters it nicely, as does Virizion. *might expand on this later if I have more time*
Happy to give VGC team rates! PM me anytime and I'll rate as soon as I can.
VGC 2013 San Jose: 2nd place Seniors Division