How bout having lost balls scattered randomly about the course. (especially in places you'd likely find em off the real links like in the weeds) These balls could be discovered while in close proximity to them, clicked on, added to bag and maybe even used as mulligans! I know I could use a bag full of them!
Maybe even have some of the suggested thrown clubs laying about in the tall grass.....I've got some clubs I never use that would be just perfect for throwing! -Neil