I like No Opening, to avoid flanking and nasty opponents getting too many benefits. I don't have the Con to use Boundless Endurance usefully (Con 12), and it's just daily, and I'm pretty sure our DM has no compunctions with confronting us with a lot of encounters a day.
For flavor reasons, I've multiclassed to ranger, and they have the potentially useful unbalancing parry, which you could use - for a feat. I don't think it's very powerful, but other multiclassing options are available too. The warlord's knights move looks useful. The wizard's shield does too (if you have the int to multiclass in the first place - and that also allows thunderwave for mass-marking). The cleric has bless and shield of faith, which look fine, and having the cleric's multiclass bonus feature implies extra healing, which is always good!

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.