For style reasons, you should pick the greataxe for a half-orc barbarian.
Power Attack is a must, of course.
The Rage feat chain doesn't seem very useful to me (only Extra Rage if you multiclass).
Cleave is very good. Great Cleave isn't something I'd waste a feat on. Situations, where this is really useful tend to be rare, or it just doesn't make a difference in the end.
Combat Expertise + Improved Trip is an obvious choice for a high strength barbarian. Trip is probably the most advantageous combat maneuver in 3.5.
Improved Critical can be bought via Keen, so isn't really needed. Weapon Focus is always nice to have, but you just have so many feats.
Close Quarter's Fighting is also good, since you rely on a non-light weapon, grapples will be bad.
Karmic Strike can also be pretty nasty, especially combined with Combat Reflexes and Improved Trip.
Now for something completely different, Iron Will is a very good feat choice, or Track might be worthwhile.
And don't forget to put a high stat on Con. You'll need it.
Bye
Thanee