Ways to lower AC for fun and profit

[Bobby M]

For an upcoming one-shot I'm building a level 9 character, and I am looking for ways to lower his AC to gain benefits, My idea is that if I hit hard enough and am easy to hit, I'll effectively be tanking for the party. Currenty, my build is duneon crasher fighter 6, Barbarian 3. I have the following already:

Shock Trooper (Feat)
Reckless Rage (Feat)
Khyber's Rage (Feat)
Vulnerable (Flaw)

So, when charging, raging, and power attacking, I'm going to have an AC modifier pf -20. giving me an AC of -10+dex modifer.

My question is are there any feats or magic items out there that will allow me to trade more AC for more bonuses?

[Necroticplague]

Robilar's Gambit gives enemies +4 to hit you, which is like an AC penalty. In exchange, you can make an AoO against anyone who attacks you.
Being Prone gives you -4 to AC against melee attacks (though +4 against ranged attacks).. No particular benefits, but here for completion's sake.

[Bobby M]

While getting more attacks would be awesome, it requires a BAB of 12 and I'll b starting at 9. I did find Karmic Strike while looking it up, which is effectively the same thing, but that requires dodge and I'm not sure if I'm willing to burn a feat for it. Thanks for the tip, anyway!

[KillianHawkeye]

Reckless Offense is a feat from the XPH (although it doesn't require you to use Psionics at all) which basically gives you the reverse of fighting defensively. You can take a -4 to AC for a +2 on attacks for a round.

[LordOfCain]

Can you have a NEGATIVE A.C.???

[Bobby M]

Can you have a NEGATIVE A.C.???

As far as I know? I know the character is gimmicky, but its a one shot and I'm gonna have a blast being easier to hit than the ground.

[John Longarrow]

So you are TRYING to play Wimp Lo from Kung Pow, enter the fist?

My nuts to your Fist maneuver!

[Inevitability]

If the group has a wizard/sorcerer, ask him to take a Huitzil familiar who then continuously distracts you.

[Fizban]

If you can fit in a level of Warblade, Punishing Stance gives you -2 AC for +1d6 on all melee attacks, all the time. You can also grab Rabid Wolf Strike at IL 3 (so take the Warblade level as your 5th character level), which gives +4 attack and +2d6 damage on the one strike attack, and also -4 AC until the start of your next turn. You could also get the strike and/or possibly the stance (depending on DM reading) via magic item, or feats, but Barb 2 is good enough and you can get +2 rages from a feat instead.