If you have Flygon with "Sand Slammer" active, but the opponent has Serperior with "Royal Heal" in play, which Ability goes first? The one that places damage or the one that heals damage?
In this situation, the player whose Pokemon are being affected gets to choose the order of when the abilities take place.
Source: TPCi Rules Team (2012-11-01)

Relevant cards

Note: All applicable cards may not be listed below.
BW1_6