I had a guy brake into my house and sleep on my sofa one night when I was out, I came home at 6, woke him up and we both had a full English. It turned out the fella was just so drunk he couldn't see that he'd walked in the wrong house for a one night stand with someone who he'd been given the name and number for previously, realised the house was empty and jumped on the sofa and I must've left the door open or something.
So according to your poll, none of those, I'd make him a cuppa and send him on his way. No one would do that without a reason, he's obviously just too far from his home (if he has one) to just pop in for a shower.
EDIT: my examples probably not one to take, I live in an area which everyone looks out for eachother, and the Police tend to avoid coming down my way.
But since I've taken a look at other posts everyone on here is really really trigger happy, why would you grab a bat and go to town on a person having a shower? It's only a shower... Maybe it's a Brit thing to offer cups of tea to avoid confrontation. But a tea sounds far better than a fight which there's a chance of loosing and getting beaten up by a lubed up naked dude.