The Canon EF 50mm f/1.8 II lens is a great lens for many different objects and can be used for portraits and landscapes with equal success.
The Canon EF 70-300mm f/4-5.6L IS USM Zoom lens is a great lens! I don’t own this lens but have tried it – if used right it takes very high quality images.
If you are looking for the perfect super wide angel zoom the The Canon EF 16-35mm f/2.8 L II is the answer. The wide angle zoom lens is what I consider one of the most important wide lenses in Canon’s line up.