I'm playing a Dragon Fire Adept Kobold, and the Slight Build feature made it seem like I could share a space with a party member.
Slight Build: The physical stature of kobolds lets them function in many ways as if they were one size category smaller. Whenever a kobold is subject to a size modifier or special size modifier for an opposed check (such as Hide), the kobold is treated as one size smaller if doing so is advantageous to the character. A kobold is also considered to be one size smaller when "squeezing" through a restrictive space. A kobold can use weapons designed for a creature one size smaller without penalty. However, the space and reach of a kobold remain those of a creature of their actual size. The benefits of this racial trait stack with the effects of powers, abilities, and spells that change the subject's size category.
So I could share a square with my fighter and use my breath weapon against the enemy without hitting my fighter?