The typical champagne blend is of three grapes - Pinot Noir, Chardonnay, and Pinot Meunier. Wines labeled as 'Blanc de Blancs' are by definition all Chardonnay, and wines labeled as 'Blanc de Noirs' contain Pinot Noir, Meunier or both in the blend.
There are how ever three additional grape varieties planted (Arbane, Petit Meslier and Pinot Blanc) and used in Champagne, they could be called legacy grapes and do not represent significant portion of the grapes used (<0.01%?). It is not permitted to plant more of these varieties.
However, sparkling wines that are not Champagne (i.e. not grown in the area legally allowed that name in France) may be made of several other grapes, too. For example, Markko Vineyards 'Excelsior' was given the name 'Champagne' with tongue-in-cheek, as the winemaker has embarked on a program to educate his consumers away from the use of the 'C' word. This wine is actually made like many German Sekts, from Riesling.