When a person is described this way, what does it mean to you?

That they murder anyone who stands in their way! *lol*

Maybe a little extreme, but it certainly doesn't sound very pleasant.

The phrase originated in war. A person who takes no prisoners is a person that kills all of their enemies. They don't capture any and imprison them, they just do away with them.

don't hurt me BATTLEAX!....please.....

Whilst I think the above gives a literal answer, I would say a person who 'takes no prisoners' would be one who would stand for no nonsense and be brutally honest in their dealings with others even if their words hurt those around them. It could also indicate some who perhaps lacked tact.
Kitty

EZMoney!

I agree with Amanda ...

'They show no mercy' ~ often pertaining to war battles; leaving no-one standing at the end. It's a 'Fight to the Death' ... like she said, they don't want to take home any prisoners.

When referring to a specific person ~ they have a hard shell and tough personality (showing no mercy or compassion for others).

It certainly has negative connotations but it can also be appropriate- and positive- when it comes to not accepting any excuses for failing to achieve something.

Why do you ask?

To me, it means that the person will do whatever they need to reach their goal - even if it means harming others on the way (emotionally or physically).