A slight do-over of szilard's suggestion.
Practiced Warrior [General]
Prerequisites
Proficiency with martial weapons, weapon focus, at least 4 levels in a full-BAB class,
Benefit
Your base attack bonus increases by one, but cannot exceed your hit dice.
Special
You can gain this feat multiple times. Its effects stack.
A fighter may select Practiced Warrior as one of his fighter bonus feats.
====================
Now only warrior types can really take it. It is more powerful than weapon focus (or GWF) but generally less powerful than the mastery feats (at best you get an extra attack out of it at -5 in addition to the +1 overall). It's nice, if IMO, a little weak.
There is an argument for +2 BAB instead of +1, but that is a bit much. Humm, perhaps a follow-on feat that requires this one and gives a +2 BAB, that would be 2 feats for +3...
Mark