Snake Beater Achievement
Get caught by Otacon stimulating yourself
This is a Metal Gear Solid 2 achievement.
During the Tanker Chapter, go to Deck A's locker room and find the sexy poster in one of the lockers. Use First Person View while outside the locker (the locker's door must be open) and look at the poster until Snake gets excited. Immediately call Otacon to trigger a funny conversation and get the achievement.
Refer to this video for further assistance: