Went to watch local derby - ice hockey - Lausanne v Fribourg Gotteron in top Swiss league. Absolutely superb. Arena virtually full with 8,000 bodies. Incredible atmosphere with non stop singing and chanting from both teams' fans. Home team won at last gasp, in a game which could have gone either way.
Equipment: Cash - tickets very expensive.
The lake Leman offers you a wide array of water sports possibilities: sailing, waterskiing, diving, etc.
The water temperature tends to be cold even in the Summer though, as the lake is fed by the glaciers around...
Equipment: Many places on the lakeside rent sailing and motor boats, as well as all the other equipment you need, like waterskis for example.
Lausanne has many ski resorts nearby to go skiing or snowboarding. The ones in its canton, Vaud, are the closest ones, which enables you to go just for the day: Leysin, Villars, Les Diablerets, Chateau d'Oex.
A little further, and thus better for at least an overnight stay are the ones in Valais where the best and bigger ski resorts are: Verbier, Crans, Nendaz, etc.
Equipment: If you did not bring your skiing or snowboarding equipment, you can easily rent everything you need in all the resorts or in Geneva itself before you go.