This one is easy! River Sand is basically a solve all solution to a lot of common problems. River Sand is a great material because it's very dense, filters water and is full of nutrients and minerals (not weeds). 

You can use river sand for many different things, here are a few but not limited to these by any means. You can fill low spot in your yard or completely redo or level your yard. It's a great base for sod and planting new grass. You can use is for a base for a driveway, road, parking lot and so on. If your yard is constantly muddy and soft, throw so river sand in those problem areas to make it dry and hard to walk on.