Attack Recharge (4e Feat)
From D&D Wiki
Through concentrated training you learn to make better use of one of your encounter attack powers.
Benefit: Choose an encounter attack power you know of lower level than your highest level encounter attack power. That power gains Recharge 6. You may select this feat multiple times. Each time its effects apply to a different encounter attack power you know.
Special: Recharge 6 allows you to roll 1d6 at the beginning of your turn. If you roll a 6 on the die, you regain the use of that power for the encounter until you expend it again.
If you retrain the power you have focused on, this feat automatically transfers to the new power.If you replace the focused power with a higher level power, this feat transfers to an available legal choice. For example, if you have Attack Focus for your level 1 encounter power, then replace that power at level 13 with a level 13 encounter power, this feat will automatically transfer to one of your other encounter powers (your level 3, 7, or 11 power, but not your level 13 as it is your highest level encounter power).