
There are roughly 1200 fatal, firearms-related accidents each year.
The large majority involve rifles and shotgun; there are under 500
fatal handgun accidents each year. I really doubt all of those
occur while the pistol is holstered, so the number of "self-inflicted
gunshot wounds by people wearing thigh holsters" is probably
well under 250 per year.


Handguns designs have included a "hammer block" since around 1960
or earlier. This is a metal part which physically seperates
the cartridge and the firing pin: Even under impact, the gun
cannot fire. The hammer block is connected to the trigger and
is pulled out of the way as the trigger is pulled. As a result,
modern pistols can fire _only_ if the trigger is pulled (or 
in some cases, if they are cocked by hand and then dropped.) 


I don't know about animal attacks, but there are 23,500 murders 
each year and under 500 die in the manner you suggest. If only
2.1% of the murders were killings by "wacko"s, you would be
wrong. Worse, there are also 102,500 rapes and 1,055,000 aggravated
assaults each year. These numbers make violent attacks, and 
preventing them, thousands of times more significant than the
accidents you are worried about.

(These figures, by the way, are from the FBI's "Uniform Crime
Report" for 1990. I'll stop by a library tomorrow and look at
the "National Crime Victimization Survey", which is more
specific about where and when the crimes occured.)