Here is a quick little workout that can be performed in a busy gym without the need for equipment.
It's called the "Jack of All Trades" workout and I got this idea from a book called High Intensity 300.
It is short but can be very tough depending on your fitness level.
You will work every muscle group from legs, to chest to back to arms.
To progress this workout you can add another exercise in for 15 reps or you can complete more rounds or simply beat the time each week.