I know it is a bit cold to think of this type of thing, but oh well. Water balloon fights are always a blast but filling and tying the balloons is always a challenge. For some reason an invention to tackle this "problem" took a loooong time to make it to an actual product.
Tie-Not has two products a knot tying wand and a balloon filler with a built-in tie-not holder. You really have to watch the video after the break to understand this product. Long story short, I wish I had this when I was on the roof of my dorm throwing balloons an incoming freshman. Would have really sped things up.