At the beginning of each combat, choose first strike, vigilance, or lifelink. Creatures you control gain that ability until end of turn.
1/24/2013 You choose which ability creatures you control will gain when Angelic Skirmisher's ability resolves. This happens before attacking creatures are declared.
1/24/2013 Only creatures you control when the ability resolves will gain the chosen ability. Creatures that come under your control later in the turn will not gain the ability.