From the Super Mario Wiki
Fencing is a class of events that appeared in Mario & Sonic at the Olympic Games. It includes only one event, Individual Epée, and is located in the National Conference Center's Fencing Hall. The Event reappears in Mario & Sonic at the London 2012 Olympic Games with a rival battle against Eggman Nega. In this game, the character is controlled by tilting the Nintendo 3DS, or by using the Circle Pad.