There's a lot of talk about what glass to use when tasting whiskey, and it's a valid (if geeky) conversation. Just going for a drink? Use anything that holds liquid. If you're out to taste whiskey, the shape, material, and size of the glass will make a difference. You can easily do a taste test with some friends by putting the same whiskey into three differently shaped glasses to smell and taste how the shapes can affect the experience.
A whiskey from a shot glass will taste slightly different from the same liquid in a wine glass or a whiskey snifter. Depending on its shape, the glass will hold the alcohol and aromas in distinctive ways, and because smell is a large part of how we taste, the glass affects the entire whiskey experience.
In general, your best choice is a tulip-shaped glass designed specifically for whiskey tasting. It will help to concentrate the aromas precisely where you stick your nose into the glass.