ahh... that question. I remeber having asked that many years ago.

Anyways, Potassium Permanganate, A.K.A. KMNO4 or condy's cristals.

It is suppose to work as a anti-fungal, water disinfectiction, disinfection solution for wound cleaning, fire starting with sugar by fricton, fire by mixing it with anti-freeze, snowmarker (big purple stain) and some other uses.

Disadvantages is it's oxidising behavior. It will cause burns on skin if its not diluted enough. Getting it in to your eyes, means a very likely chance of getting permanent blind.
The dosage for waterpurification is very low. About 2 crystals per quart. Making it very hard to dose in the field.
Making fire with is is really not very easy or practical, considering the alternatives.

So yes it has many uses, but it does none well and is a safety hazard.

Also it's ability to purify water is not full researched.