Wotcher
1. An exclamation of surprise, chiefly British, meaning the equivalent of "watch out" or "watch it".

2. When used nonchalantly, can also mean something similar to "take care", or "good luck".
1.
James: (upon nearly stepping in a pothole)  Wotcher!

2.
Greg: I've got three exams tomorrow.
James: Ooh.. wotcher.