Here's a little diddy by Michael Hernandez. How about this for spot on?

1. If I like it, it's mine.
2. If it's in my hand, it's mine.
3. If I can take it from you, it's mine.
4. If I had it a little while ago, it's mine.
5. If it's mine, it must never appear to be yours in any way.
6. If I'm doing or building something, all the pieces are mine.
7. If it looks like it's mine, it's mine.
8. If I saw it first, it's mine.
9. If I can see it, it's mine.
10. If I think it's mine, it's mine.
11. If I want it, it's mine.
12. If I "need it, it's mine (yes, I know the difference between "want" and "need"!).
13. If I say it's mine, it's mine.
14. If you don't stop me from playing with it, it's mine.
15. If you tell me I can play with it, it's mine.
16. If it will upset me too much when you take it away from me, it's mine.
17. If I (think I) can play with it better than you can, it's mine.
18. If I play with it long enough, it's mine.
19. If you are playing with something and you put it down, it's mine.
20. If it's broken, it's yours (no wait, all the pieces are mine).