Persistent Attacker

(Complete Scoundrel, page 80, DnD 3.5)

[Ambush]

Once you find a target's weak point, you can easily strike it again.

Benefit

If your sneak attack hits, your first attack against that creature on your next turn is also considered a sneak attack even if it wouldn't normally qualify. Using this feat reduces your first sneak attack's damage by 4d6. The resulting second sneak attack deals its full extra damage.