Keg is one of the last of a breed of cards that
will hopefully never be printed again. Artifact
removal cards have slowly been phased out, but its
only because they were overly powerful. This and
Nev's Disk allowed Blue to dominate for too long.
In Constructed, easily a 4, in Limited, most
likely a 2.5.
Bill (aka Pojo)
Keg was a good card for the blue mage to keep on
hand to deal with enemy permanents that make it
past your counters.