The Brawler is the only pure martial that can keep up with 4th level and even 6th level casters.

[Malik Gyan Daumantas]

I am thoroughly convinced of this after playing around with the brawler a bit more. No other Martial class comes close to offering what Martial flexibility does, the ability to adapt your combat style on the fly is absolutely insane.

Like for example this build I have I wanted to have a focus on the fundamentals (Striking and Grappling) With Flickering Step giving much needed mobility.

Improved Unarmed Strike
1.Improved Grapple
Bonus Feat 1:Pummeling Style
3.Savage Slam
5.Unbalancing Blow
Bonus Feat 1:Dazing Fist
7.Greater Grapple
Bonus Feat 1:Pummeling Charge
9.Flickering Step
11.Dimensional Agility
Bonus Feat 1:Dimentional Assault
13.Dimensional Dervish

This is what I qualify for via martial flexibility and im pretty sure i didn't get everything.

Whirling Hold>Overhead Flip>Savage Leap
Scorpion Style>Gorgon's Fist>Medusa's Wrath
Dodge>Mobility>Spring Attack
Combat Reflexes>Disruptive>Spellbreaker
Improved Trip>Improved Reposition>Pummeling Bully
Combat Reflexes>Vicious Stomp>Stunning Fist
Power Attack>Improved Bull Rush>Hurricane Punch
Step Up>Following Step>Step Up and Strike
Weapon Focus(Unarmed Strike)>Dazzling Display>Dramatic Slam
Weapon Focus(Unarmed Strike)>Combat Reflexes>CounterPunch

Wolf Style>Wolf Trip>Wolf Savage(Trip and Rend)
Tiger Style>Power Attack>Tiger Claws(Twin Strike)
Snapping Turtle Style>Snapping Turtle Clutch>Snapping Turtle Shell(Counter Grapple)
Kraken Style>Kraken Throttle>Kraken Wrack(Squeeze em)
Janni Style>Janni Tempest>Janni Rush(Charge and Free Bullrush/Trip)
Dragonfly Style>Dragonfly Wings>Dragonfly Flight(Parkour Combat)
Boar Style>Boar Ferocity>Boar Shred(Rip and Tear)
Bull Catcher Style>Bull Catcher Toss>Bull Catcher Wrangler(Grapple and Divert)
Improved Dirty Trick>Kitsune Style>Kitsune Tricks(UnderHanded)

This gives me so many different options when it comes to adapting to every situation and due to being able to use disruptive and spellbreaker you can teleport to that cocky wizard in the back and just ruin their day. No other pure martial even comes close to this level of adaptability. I honestly only realized this after messing around with the shifter and realized nothing i could do with that could compare.

[Claxon]

I mean your options are:
barbarian
fighter
monk
rogue
cavalier
gunslinger
vigilante
brawler
slayer

While martial flexibility does indeed make you flexible, you actually have to be very knowledgeable about feats and the situation you're in to make use of it. It's actually hard to play.

Probably 80% of people use it to get the same set of feats each combat.

As to the value of the different combinations you pointed out...to be honest I don't know. Probably I don't need them most of the time. You can probably play a raging pouncing barbarian and get your job done 95% of the time, and the other 5% you ask the wizard to cast fly on you first.

[Name Violation]

My favorites for martial flex:
Dedicated adversary
Rat catcher
Ghost slayer

[MrCharisma]

Bralwer is great, but I think 1 pevel of Bralwer gets you about 80% of the versatility, allowing you to use another class with other benefits that scale better or even enhance your flexibility.

Eg. Brawler-1/Barbarian-X. Brawler gets you Martial Flexibility 4/day and Improved Unarmed Strike. Barbarian gets you damage and stuff, but also the Strength Surge rage power. So 4 times per day you have an "I Win" button on your preferred combat maneuver (it's usually Grapple). I use this along with Combat Expertise (I wanted it for Improved Stalwart, but it's also useful for prerequisites) and it gives me a huge amount of combat versatility.

[DeathlessOne]

Eh, the Exemplar Brawler is my preferred archetype for the class. Fills in that 5th wheel force multiplier niche while still being quite capable of adapting to just about any combat scenario. Tack on a decent VMC option and select some Item Mastery feats (and Use Magic Device), and you've got a solid chassis for just about any occasion.

[Temperans]

Basic shifter is basic but effective. Where it really gets interesting is the archetypes.

Being able to shift into a flying creature with boosted natural attacks from shifter will wreck most casters. The high will and fort save makes it so they will rarely get affected, and getting evasion is trivial. Everything else is just gravy.

Yes martial flexibility is an amazing ability and brawlers can do some crazy stuff. But they are not the only one that can keep up. Case and point being vigilante which has many tools to deal with various issues.

Not to mention things like Supersitious Barbarian, Monks stunning fist/abundant step/dimensional feats, Shield Fighters being beef, Paladins have the best saves period, etc.

[Mysterious Stranger]

Like Claxon mention it takes a lot of system mastery to take full advantage of martial flexibility. It also depends on what sources the GM is allowing.

Martial flexibility also normally uses a move action to gain the feats. This means the brawler is limited in what they can do on the first turn. Style feats also require you to use a swift action, and cannot use them before combat. Also don’t forget that each individual feat counts towards the daily limit. So if a 10th level brawler replaces 3 feats it counts as 3 uses. That means the 13th level brawler can only replace 3 feats 3 times per day.

[Azothath]

I think the GM & Player need to make a list of Feats for Martial Flexibility (like spells for a wizard) with the PC rolling each level to gain another. It simplifies the selection and lets both know where this is gonna go and that it will work within Game Balance so there are not a lot of surprises(and arguments) and book flipping at the table.
This method clarifies the options of what to pick on demand. There are a lot of feats the PC won't meet the requirements for and this method eliminates all of those from the start. It's also possible to review what spells might open up as options.

[Claxon]

Azothath, at first I was going to disagree but as a GM I wont let a player sit for a long time looking up feats at the table wasting everyone's time. So I would be likely to say they delay, and if they take too long they simply skip their turn.

With that in mind, telling the player to create a list of feats they qualify for and would like to use does seem like a good idea, though I don't know that I'd absolutely restrict them to that list, I would tell them that not being able to quickly decide on a feat would see their character delay or possibly lose their turn.

[Mysterious Stranger]

I would encourage a player with marital flexibility to come up with a chart of options but would not restrict them to it. I would however put a time limit on how long they can take, if they go over that time limit, they have to either take something from the premade chart or not use the ability. About a minute or two at most sounds like a reasonable limit. The same limit should also apply to other players making their choices.

[Greylurker]

If you have some of the Martial Focused handbooks (those little thin books Paizo did; Weapon Master, Armor Master, etc...) the Fighter gets a lot of things that pull it up. Big ones being Focused Weapon (gives you War Priest damage with you main weapon) and Warrior Spirit (Lets you enchant your main weapon and give it magic weapon properties)

[Claxon]

Focused Weapon is really over rated, IMO.

Like if I have the free feats/wepon training to spare and I'm (for some reason) using a weapon with a low damage die I'll consider it.

But like, you're going from at worst a d4 weapon to at best a 2d8 weapon.

That's 2.5 avg damage vs 9 avg damage. So it's an average of 6.5 more damage. Which isn't terrible, but it seems like more to people because of the dice rolling.

But most of the time people aren't using crappy d4 weapons. We're using like d8,d10, d12 weapons and so the value becomes less and less.

Armed Bravery (assuming you didn't trade away bravery in an archetype) and Warrior Spirit are my first two choices generally because they're both super powerful for the fighter chassis.

There other great choices, but mostly for making a combat style that doesn't work well into a good combat style.

[Greylurker]

Worked well for me because I was using it for a two weapon Dagger fighter, so yeah d4 to 2d8 was very nice to do when combined with the Two-Weapon fighting tree. Added Trained Grace to double the Weapon Training damage bonus and Warrior Spirit for that flexibility enchanting weapons.

[Temperans]

Yeah Focused weapon is mostly a fix for 1d3 and 1d4 weapons.