I agree with TobiSGD re '~'.
I can generate this
Code:
sds
dssd
sdsd
d
sd
s
d
d
@
@
@
by simply ensuring that the "last line" is longer than will fit in entirely into the current terminal size of the vim session.
In actual fact, its just a long bunch of 'a' chars.
If you setup a longish line, then resize the height of the session using drag/drop on the bottom of the window, you'll see what I mean.
HTH