I learned the hard way to make a thumb drive that contains Ccleaner, Malwarebytes, Avast, Defraggle, and a couple other pieces of software to combat all kinds of nasties...I call it "MasterKey". And it hasn't failed me yet...I might make a couple for some friends as gifts.
On another note, we used to write harmless viruses to mess with each other that usually involved changing someone's homepage to meatspin or something like that, or play a dancing pirate or monkey crapping on a banana...really juvenile stuff. But it was always fun to see their faces when it was discovered.