Oh. It seems to have resized. Weird...
Anyway the reason I didn't use a circle tool is because the program I used doesn't have one! I guess we could say it's auto-aim.

I told my brother to aim it at my other brother, but he said that the homemade was kind of heavy and hard to position. (He's only 11.)
I usually do use water balloon icons, but like I said before, the program didn't have a circle tool, so I decided to make it so he had no water balloons left. There normally would be water balloon icons there if he actually had any (Like in the first pic.). I have an idea for a reservoir/PC gauge, so that will be better next time as well.
The only reason I thought they would be cheap, is because of the superior range and power. If I designed a WW FPS, I certainly wouldn't make it so you had to push a button to shift your hand between the valve and pump, I'd just make it so when you pushed the fire button, your hand would automatically shift to the valve and fire. (In the case of this homemade of course. Some homemades have regular triggers.) Also, I don't think pumping while shooting matters that much. In real life, I hardly ever pump while I shoot, preferring to take tap shots and only pump when needed.
Are you saying that you were going to make a WW FPS game? That sounds cool.