Can't believe none of the "men" here are man enough to say:

Best: can have sex with women mostly for a bit of charm and some none-commital noises pretending to have heard and absorbed every word they say.

Worst: Periods because all negative points mentioned in this thread are 10 x more bad during this monthly occurrence whilst all positives apart from use of mouth for pleasurable things are either off the menu or disgusting. However, use of mouth must be done correctly.