I'd like to be able to hide behind things. Not joking.
Like if you have a blaster, you can peer around a corner, fire off a few rounds, then jump back behind it. I've always thought it was stupid how everyone just stands in a line and shoots at each other. Maybe boxes and crates could at +1 to defense, while something more solid would add +2. They could also throw in some feats to add to the bonuses.