Remathilis
Legend
A reserve feat is a feat tied to a type of spell, and it allows you to do magic at no real cost to you indefinitely. For instance, there is a reserve feat that allows you to cast a fireburst that does 1d6 per the level of your highest memorized fire spell. So if you were a 5th level wizard with fireball, as long as you didn't cast your fireball (and get 5d6 fire damage in a huge radius) you could every round do a mini 3d6 fireball in a small radius. There were feats for lots of types of spells, healing, summoning and teleportation being the most memorable to me. My DM banned them for being to powerful, so I don't know how they play.
Jay
Honestly, I've allowed them and so far, they don't seem too broken. The biggest problems is they are supernatural powers (no SR) and the polymorph-based one is a bit broken (basically at-will temp hp to self). The fire-one rarely does any major damage, and allows the wizard to feel more "wizardy" by always having a spell to use (until he fires his high-level big gun).
The healing one, btw, only heals up to 1/2 max hp, so all it does is guarantee everyone has 1/2 hp after every fight. Cure spells and wands are still cheaper ways to full-heal.