I love the reserve feat Winter's Blast. I have a druid in a game I never got to finish who fought almost exclusively with that, she used most of her spells for buffing but always kept a single slot at or near her highest level prepped with an ice spell to spam that whenever she had a spare action.

I also love Slashing Flurry and a lot of the Fighter feats that got introduced in the same book, its a shame theyre fighter only and have such silly and weak prereqs.