Probably one of the most recognized symbols in the entire world, the Nike logo was created in 1971 by Carolyn Davidson, a graphic design student at Portland State University. This is a great image, because it doesn't need a single letter to convey the message of speed, or swiftness. The Nike "Swoosh" also works in color very well and it can even be emblazoned on the side of the product itself, a sneaker.
The Pepsi cola logo has gone through many changes in its long history that spans over a hundred years. The circle, with the wave in the middle, made its first appearance in 1962. The logo also lost the brush stroke look it had for about 50 years and went with the sans serif letters we all recognize the most. I believe this logo is effective because the wave in the circle is very simple and perfect for picturing liquid in a can or bottle. The new slant and rounding of the letters 'e' and 's' can carry over this roundness to the overall piece.