I think the formula for Sharp Legs might be wrong? I have 4 points into it, but the damage numbers only say *8, instead of the expected *16. Maybe instead of 2^X the code is accidentally using 2*X?
@KingsfordCat: "Collision Damage" is when a boss or enemy come into direct contact with the droid itself. Also, the droids can eat a bullet for you, but after they disappear for the "recovery time" amount of time before they can take another.