I haven't walked into the edge of an open hatch...yet, but two headbangers
for me are:

1: moving briskly and happily in through the sliding door and quickly
standing up only to find that one's spouse has unfolded the top bunk and is
holding it down with her body weight as one's head makes contact...

2: again moving briskly into the van through the sliding door but for some
reason mis-timing one's "straightening up" and cracking the top of the skull
on the the door jam.

Both can make your say things you'll regret, but I think #2 provides the
sharper, more exquisite pain.

Alistair