Whipkeeper    2RR
Tap: Deal X damage to target creature where X is the amount of damage
it has been dealt already this turn. 1/1
Well, this is a really expensive 1/1 i agree. And to be honest it might not exactly look that impressive. How long would a measly creature like that stay in play. Well these are things that can be handled. 
If you are playing a draft or sealed deck event at a local store or with friends this is a great card to use. This card is the answer to all those times when they have that annoying 3/3 flier and all you have is a SHOCK. Also, if there is a 4/4 KAVU TITAN on the other side of the board, look at that, my GRIZZLY BEARS kills it. YAY!!!
The way to play this card is either in a straight red deck that relies on direct damage or in a green deck that splashes red for SHIVAN WURM and such. It is great in a red deck because all of your direct damage spells towards a creature count as double. A SEAL OF FIRE can now kill that new kids AIR ELEMENTAL that has been providing beats for the last 3 turns. Also, it can work to enhance your little creatures damage.
This card is ideal in a green deck because it will stay alive, comes out quicker, and doubles the power of a creature when blocking. Don't you hate it when your bear was serving as beats when your opponent drops a pesky wall. Well, now, just don't worry about wasting your last GIANT GROWTH, WHIPKEEPER to the rescue.
This card is much better in limited as there are less ways for your opponent to get rid of him. I strongly recommend using this card if you are anywhere near playing red in a limited deck. 
In constructed this card is just mediocre because there are other cards that can serve you for a cheaper, more effective spell.