Till now I have completed the short tutorials of some basic tools of creo Elements/Pro and I think on the basics of those tutorials you can make some of part that looks interesting.
For a simple exercise
Try to make a piston without connecting rod you have to select the dimensions by yourself or you can use the dimensions shown in fig .
But I am giving you short steps:
1) Make a circle of and extrude it so it become a cylinder
2) Make extrude cut at the one end of cylinder
4) For making grooves for piston rings use Revolve tool after sketch
This test you should have to attempt first and after some days I will posts its method.