Kingdra is one neat card that's definitely been getting some wins at BRs (4 1st places last I checked). Stat-wise, Kingdra is very solid; 130 HP is just right for a Stage 2, +30 Weakness to Lightning (an uncommonly played type), no Resistance, and 1 Energy for a Retreat Cost. Aqua Stream is a neat late-game attack; for no energy, you can do 10x the number of Water Energies in you discard (then you have to shuffle them back into the deck, making it a nice one-shot deal late game). Dragon Pump of course is where he shines; for 1 Water Energy, you deal a basic 40 damage, plus 20 more and 20 to an opponent's benched Pokemon of your choice by discarding 2 cards from your hand. This lets you either get rid of useless cards or Water Energy to thin your hand for Claydol next turn.
Modified - 9/10 (Very solid card, should see lots of play this season with its cheap attacks and great HP)
Limited - 10/10 (Bring out one of these bad boys somehow and you have a very nice, cheap attack to work with)
Unlimited - 3/10 (I can see this working in some Water decks)