If you're into using the ViPR fitness system (and if you're not, you should be!) then this is a great challenge set by Gavin Attorre, personal trainer and international ViPR master trainer.
The challenge is simple - take a 10kg ViPR and complete the following exercises as fast as possible, keeping good form throughout:
10x Squat thread the needle
10x Squat to uppercut
10x Ice skaters
Repeat the circuit 3 times as fast as possible.
See the video for Gavin's demonstration of the challenge.... more details