Complete Champion has a domain wizard variant that allows you to take a domain power instead of a 5th, 10th, 15th, or 20th level feat. The luck domain has its nifty reroll anything 1/day feature. It's something I like because it's one of the few ways to reroll d100s. The mantle of second chances and pride domain have already been suggested, and if you can afford it, the amulet of second chances (both the mantle and amulet are in the MIC) lets you redo an entire round and retain the knowledge of the erased round 1/day, which has all sorts of other utility, like casting vision and undoing the round to save the EXP cost. The destiny domain from Races of Destiny has the choose destiny spell, which is incredible to persist, and it allows you to roll twice on all attack rolls, saves, skill checks, and ability checks, and take the better d20. On top of that, the destiny domain has the warp destiny spell, which can be cast as an immediate action after you've learned whether your initial saving throw failed. Warp destiny allows you to reroll the saving throw with a bonus equal to your caster level, capped at 20. Goliaths also have several racial feats in Races of Stone that may be of interest, if you're playing as a caster your DM might be willing to waive the LA, as goliath racial traits really aren't that helpful to casters.
