The last virus you'll ever run
For fun, a former colleague and I came up with the idea of a "last virus" which silently carves out space on your drive, installs Linux there, installs a window manager which looks like Windows and when complete, reboots into "Winux". Finally, it reclaims the space formerly used by Windows and adds it to the storage pool.
We had a lot of fun theorizing how it might be made to work and got a lot of laughs (some of them evil) along the way.
Any takers? (Bwahahahaha)