The following nine feats are taken from D&D books, should be easy to program, and wouldn't harm game balance.
Blind-fight: (PHB)
When attacking a creature with concealment (such as from Blur or Obscuring Mist), you roll twice against concealment-miss chance and use the better result. You suffer only one-half the speed penalty from being blinded. Also, invisible creatures attacking you may be denied certain bonuses.
(Note: this would also be a reasonable feat to allow on some magic jewelery)
Font of Life: (Heros of Horror)
You can negate incoming energy drain / negative level effects with a successful fortitude save. Use the effect's normal save DC, or the generic DC = 10 + HD/2 + cha if unknown. If the effect already offered a saving throw, you get an extra chance to save.
(Note: this would also work well as an effect on some magic armor)
Armor Specialization: (PHB2)
Requires BAB12, Medium Armor Proficiency
You gain DR 2/- in medium or heavy armor.
(Modified from D&D to be more generic)
Shield Specialization: (PHB2)
Requires shield proficiency
The shield bonus you gain from a light or heavy (but not tower) shield increases by +1.
(Modified from D&D to be more generic)
Quick Staff: (PHB2)
You gain a +2 dodge AC bonus when wielding a quarterstaff.
(Simplified and improved from D&D)
Crossbow Sniper: (PHB2)
Requires BAB1, Crossbow prof, Weapon Focus Ranged
Add one-half your dex bonus to ranged damage rolls with a crossbow. The range limit on sneak attacks with a crossbow doubles.
(For game balance, I suggest doubling the damage benefit for Great Crossbows, although the D&D book doesn't support that)
Ranged Pin: (CW)
Requires Dex15, BAB5, Point Blank Shot, Precise Shot
Activate this feat to make a trip attempt with a ranged or thrown weapon.
(Note: this ability has the potential to be situationally overpowered, but a sufficient cooldown delay will prevent that)
Zen Archery: (CW)
Requires Wis13, BAB1
You may use wisdom in place of dexerity on ranged attack rolls.
Intuitive Attack: (BoED)
Requires Good alignment.
You may use wisdom in place of strength on melee attack rolls with a simple weapon.
Game balance notes:
Overall, adding more useful feats would increase the power of the fighter class, which needs help at high level.
Blind Fight- mostly attractive to fighters who have more feat slots than they know what to do with.
Font of Life- note that Warforged are immune to energy drain anyhow, so allowing other races to spend a feat for a chance to negate the attack is not overpowered.
Crossbow Sniper- this would restore some viability to crossbow characters, who right now contribute little to combat.
Armor Specialization- this would give high-level fighters to gain much less DR than a barb, and only if they didn't already get it from adamantine armor.
Zen Archery- some clerics / paladins would be able to get good accuracy with bows, which isn't powerful because bows aren't powerful.
Intuitive Attack:
Two effects. First, low-str clerics could choose to spend a feat and become accurate with maces, which isn't powerful because they still don't have much strength damage bonus.
Second, monks would have three ways they can build for attacking:
1. Strength. No feat, applies to all weapons, and adds damage.
2. Dexerity. One feat, applies to fist and kama but not staff, adds AC and reflex.
3. Wisdom. One feat, applies to fist and staff but not kama, adds AC and will.