On a pure barbarian, I think you're kinda screwed, as even on an 18/2 fighter (what I have) the choices aren't exactly attractive.
We have 7 heroic feats, 2 fighter bonus feats, and 2 epic feats (currently) to fit in:
THF
ITHF
GTHF
Power Attack
Toughness/Barb PL
Cleave
Great Cleave
Weapon Focus
Improved Critical
Improved Sunder
Stunning Blow
Overwhelming Critical
I'm thinking Toughness ends up getting kicked to the curb. As it stands now, I only have 2 ranks each in race and class Toughness on my barb. Dropping the feat and those enhancements loses me 60 HP, and frees up 6 AP. That could be used on Barbarian Con I and II (don't have currently) for another Con bracket, or +20 HP, recouping the loss of the feat, partly, if not the enhancements (and I lose 2 Intimidate).
Can't really see dumping anything else. Giving up GTHF for OC seems silly, as you're trading DPS for DPS. Sunder would be next on my list, but I've been in too many raids (forget parties!) where I'm the only one with IS, and it's too relevant for high Fort bosses to ignore.