This was prompted by a discussion on the van of the death of Steve McNair & Sahel Kazemi. The police have determined that she killed him & then herself. This sort of thing always leads to a discussion on how dangerous women are. So, I looked up the statistics on murder by gender. This is what I found.

Most killers are men. Most people killed are men. When men kill, they are most likely to kill male strangers or acquaintances. Women are most likely to be killed by spouses or lovers.

The Lesson is:
If you are a man, it is unlikely that your wife or girlfriend will kill you. However, if she is inclined to murder you are her likeliest victim. If you beat her, your chances are better that she will kill you. In general, you are much more likely to be killed by a male stranger or acquaintance in a public place.
If you are a woman, your husband or lover is the most likely person to kill you. And, he is likely to kill you in your house or a friend’s house. Therefore, you are safest away from home and among strangers.

I couldn’t find more recent statistics, but what I did find was that things haven’t changed all that much.

The actual statistics:
While women comprise more than half of the U.S. population they commit only 15% of all murders. When women do kill they kill family members, usually men who have battered them for years. 90% of the women in jail for killing men had been battered by those men.1 Women comprise 23% of all homicide victims.
Men mostly kill acquaintances, strangers, or individuals of undetermined relationship (80%). When women kill they kill their spouse (31.4%), intimate acquaintance (13.6%) or another member of their family (14.8%).2
http://home.cybergrrl.com/dv/stat/statbwkill.html
Females were more likely to be victimized by persons whom they knew (62%) while males were more likely to be victimized by strangers (63%).
Females were more likely to be victimized at home (their own or that of a neighbor, friend, or relative). Males were most likely to be victimized in public places such as businesses, parking lots, and open areas.3
http://www.ojp.usdoj.gov/bjs/pub/pdf/sdvv.pdf

This is the best I could do. It is the only one we saw.