Set up Risk as usual. Relabel each region (there are 6) on the playing board to represent a body part. Here's a list of possibilities:
7. Other more erogenous zones
Each time a player takes control over a country in a region, they get to take control for 2 minutes of the equivalent body part of their partner. Or if the player chooses, they can request that their partner take control of that body part on them! Make sure both players determine what is acceptable up front and the both players agree to not over step those boundaries. The winner gets a full body massage!