This picture here shows two overlapping MTA logos, one that is a little more recent and one that is old, bold, and awesome. The awesome one is the giant M outline you see. Some Subway trains still show this logo on the exterior of the train and it always brings a smile to my face when I see it. It's like a forgotten part of NYC Subway history that just keeps on going and going despite an obvious change designated by the higher-ups.
Here's a much cleaner version of the logo. You can download an EPS file of it here.