Student of the Sword [Multiclass Fighter]

Prerequisite: Str 13
Benefit: You gain training in one skill from the fighter's class skill list.
    Choose either one-handed melee weapons or two-handed melee weapons. Once per encounter as a free action, you can add a +1 bonus to the next attack roll you make with a weapon of that category. Whether the attack hits or misses, you mark the target until the end of your next turn.

Published in Player's Handbook, page(s) 208.