Keep it light, try to be unique, innovative and funny. Heck, you might even come up with some valid functions some App team might implement. Just remember it's a game and have fun!!!
What model are you getting?
Price point? (Apple Watch specs | iMore)
Suggested function? (the actual game part)
42mm Watch space grey
When I pour water on it the casing should change color from the Aluminum to the SS to the rose gold. So I only need to buy one and no one will ever know which one