This is one of my best tasks and have given it to submissives in the past.

1) The sub strips completely naked.

2) A coin is placed on the wall and the sub must keep it there for 5 minutes using only his/her nose.

Note: This task can be incredibly easy or dreadfully hard. I found that I would start easily and giving a medeocre reward but to increase difficulty the sub must stand at an increased distance from the wall, obviously the sub cannot support weight with nose so the sub must raise feet to almost tip-toe height. I found the ideal distance from the wall was about 1 foot. This is a predicament postion..

3) After the given time if the sub still has the coin then reward should be given.

4) If coin falls then timer is reset.

A few additional tools can make this task alot more interesting I have used in the past a butt plug whilst standing, a vibrator is also good as it always decreases concentration of subject

The great thing about this task is it can be improvised with anything and has potential to be modified and include toys.

Required tools(minimum) :
Timer (clock, ipod, phone, watch etc...)
Coin (heavier the coin the more difficult)

Additional tools that can be used.
Vibrator
Butt plug
Nipple clamps or clothing pegs work equally well
Gag

Remember, BDSM is more in the mind so if you have an easy task then try to draw as much concentration away from the task as to make it more enjoyable, use toys at your disposal, a gag, plug and vibrator will do this and make the task that much more difficult to complete.