Thank you for the question. There are lots of career choices for Mechanical Engineers. I hope that others answer based on their experience. For me, I have been in product development for my career and I have worked on consumer products and medical. Some have been a newer version of existing products and some have been cutting edge. In medical, I have worked on a device that measures blood chemistry through the skin using light. And in consumer products I worked on the Xbox 360 wireless racing wheel.
As far as the engineers that I get to work with, the list is long. EEs for PCB design, other MEs working on the same and different projects, Software as we need to determine what electro-mechanical interfaces are needed, Test Engineers, Reliability Engineers, manufacturing engineers, and the list goes on.
I have also traveled in Europe and Asia for my projects.