Getting dynamically flexible bonus feats is really powerful and useful. Being able to dial up exactly the trick you need, exactly when you need it, is an ability that can be a godsend.
Most notably, this ability serves as the centerpiece of the Brawler class, in the form of
Martial Flexibility. A number of archetypes based on the Brawler also have it- the
Warsighted oracle, the
Martial Master and
Free-Style Fighters, the
Eldritch Scrapper.
But this isn't the only way to get flexible bonus feats. There are two spells that can be very helpful for this purpose, though both of them are somewhat restricted.
The first is the famous
Paragon Surge. While it's half-elf only and has recently been nerfed pretty hard, such that the bonus feat you gain has to be chosen when you prepare the spell and you can't benefit from two different such feats in one 24-hour period, it's still very useful.
The second is the spell
Tactical Adaptation- a 3rd-level magus spell that functions similarly to Paragon Surge, but only with combat feats.
There's the
Manual of War, a relatively inexpensive magic item that lets you trade out one of your fighter bonus feats for any other one you qualify for after an hour of study. Works for Brawlers too, thanks to their Martial Training class feature.
If you're using the
Resonant Powers rules for Wayfinders, you can flexibly get a limited number of bonus feats by slotting the relevant ioun stone into your Wayfinder on-the-go: Improved Unarmed Strike, Blind-Fight, and Weapon Focus can be nabbed through Method 1, and while that's a short list, they're all prereqs for other useful feats. If you're using Method 2, you can nab any of Alertness, Blind-Fight, Combat Expertise, Improved Unarmed Strike, Quicken Spell (!), Run, Brew Potion, Defensive Combat Training, or Fleet- though to randomly roll a significant number of these, you'd probably have to invest in an enormous sack of a hundred or so dull grey ioun stones and painstakingly test each of them for resonant powers, which might get you whacked in the head with a rulebook by your GM.
Finally, there are a pair of feats that can be useful under the right circumstances.
Barroom Brawler basically grants any non-brawler class a 1/day use of a 1st-level brawler's Martial Flexibility, though it's much less useful for actual Brawlers. And lastly, there's
Critical Versatility, which lets you spend an hour of practice to turn it into any other critical feat for an indefinite period.
You could actually go for an interesting high-level gimmick build by going half-elf Brawler 12/Wizard 7th with a Ring of Spell Knowledge to grab Tactical Adaptation. This would let you take up to *six-feat combos* at once- three from Martial Flexibility, one from the Manual, one from Paragon Surge, one from Tactical Adaptation- or *seven-feat* ones if one of them was a critical feat or among the limited list you can get from Ioun Stones.
3.5 didn't explore the concept quite as much as Pathfinder, but there's still quite a bit.
The Blood Meditation racial trait of Spellscales can get a version of Improved Counterspell, Eschew Materials, Widen Spell, Heighten Spell, Empower Spell, Still Spell usable a certain number of times per day.
The 2nd-level spell Heroics gets the recipient any one fighter bonus feat, and isn't subject to the one-at-a-time restrictions of its Pathfinder equivalent.
The 2nd-level spell
Mirror Move gets you 1 + your Intelligence modifier bonus feats from one casting (!), but it has to be 'any general feat with an obvious physical effect that you observed another perform within the past 10 rounds'. Best if you've got multiple party members with totally sweet feat chains, or if you frequently fight fighters and the like.
The 2nd-level power
Feat Leech can
steal feats from others, but they get a save, and it only works on psionic and metapsionic feats.
There's also the 2nd-level ability of the
chameleon prestige class, which is just a bonus feat changeable at the start of each day.
Lastly, there's the Weapon Aptitude class feature of the Warblade, which lets you trade out weapon-specific feats like Weapon Focus and Improved Critical for the same feat focused on a different weapon by taking an hour of practice. Especially handy for Exotic Weapon Proficiency.
Are there any sources of flexible bonus feats I've missed- archetypes, feats, class features, items, spells, something else? Anything in widely-accepted 3rd party material like DSP? Does this inspire anyone to come up with some interesting builds?
