How about a - so you can close a window down to the task bar, oops it also needs a task bar, but then again one of the nice features I like about one of its music players is that if you close it it turns itself into on icon on the screen which saves space for more windows, if this can be incorporated into ever program that opens up something on your main screen it would be cool.
At first I was going to say an R.I.P. on a gravestone, but as we all know that isn't true, maybe for macs but Amiga's no.