Tunnelfighter (4e Feat)
From D&D Wiki
You can fight more naturally in the cramped and close quarters of caves and tunnels than usual.
Benefit: You ignore the attack penalty for squeezing or being in a narrow or low space when attacking with a light blade, spear or polearm, and the attack penalty for squeezing or being in a narrow or low space is halved when attacking with a two-handed weapon. In addition, the attack penalty for being in a narrow and low space space is halved.