Armorless Fighter (3.5e Alternate Class Feature)
From D&D Wiki
You rely on your skill and strength of arms to protect you, rather than encasing yourself in steel.
Replaces: Armorless Fighter replaces proficiency with all armor and shields, and precludes ever gaining proficiency with them, even through multiclassing (the character must be proficient in light, medium, and heavy armor to start with). Your AC may never be modified by magic in any way, the only exception being permanent increases to ability scores. Special feats that modify your base AC like Vow of Poverty do not stack with Armorless Fighter.
Benefit: Instead of adding armor or shield bonuses to your armor class, you add your Fighter class level to your AC. You lose this bonus if you are armored, wearing a shield, carrying a medium or heavy load, immobilized or helpless. This bonus to AC applies even against touch attacks or when flat-footed. If you are not flat-footed, and are holding a weapon for which you have taken the Weapon Focus feat, you also add your Strength bonus to your AC.
Note: Your Strength bonus only applies to melee attacks made by creatures of no more than one size category larger than you, and does not apply to touch attacks.