Brawn
Allows you to carry heavier objects in your inventory, increases some damage on a lot of weapons, or attack speed in the case of pistols and rifles (and more exotic, science devices).
Where to train
Brawn can be trained on the weight sets found in gyms. Brucie's Gym in Corpclave has one that can be set all the way up to difficulty level 8, while Rolf's Gym in Slagtown can only go up to 5.