For me workplace touching (let alone tickling) of a member of staff by another is usually a form of bullying and dominance of the person being touched, and means of showing off to other co-workers. Magnify all of the above if it is by a senior member of staff.
A lot of guys don't seem to get this, so I would say imagine if the boot was on the other foot. Only instead of a woman touching and tickling you, make that your 6ft 6inch gay male supervisor. You might laugh if you were unexpectedly tickled by him, but I am sure you wouldn't find it funny.
If touching and tickling is welcomed then make arrangements for it to take place outside of work. After all even if it is enjoyed by the parties involved, it can be embarrasing and distracting for co-workers in the vicinity.