In my extensive experience gleaned by watching my network I can give you are pretty accurate answer. In order of volume highest to lowest:-

1. Shopping, (often for shoes).
2. Personal Banking
3. Checking horoscopes.
4. Reading inspirational material from religious web sites
5. UDP, (the DNS requests for the above activity)
6. ARP - this is rare and is only seen when the user turns on the computer. After that no local assets seem to be used.

Laughing??? Don't... It's a fact!!!!