Usual clocks will suffice your needs to know the time but, usual is just usual and sometimes it becomes too usual. If you need a change then there is a few of pretty unusual clock designs which will completely change the way you are understanding your time.
One of such unusual clocks is this verTick clock designed by Gavin Henderson.
The clocks is made of three simple bars with numbers written on them. And there is one frame where you need to watch to see what time is it. The bars are moving up and down. One bar shows hours, other two are showing minutes. This clock is one of those which will tickle your guests minds for a while untill they learn how to watch time on it.