What is the official sidearm/field weapon (if any) of these agencies:

FBI, CIA, NSA, SWAT, NAVY, Navy Seals, ARMY, MARINES, AIR FORCE,
Secret Service, Isreali Mossad, Interpol, MI5, FFI, DGSE (french).

To clarify, I want to know what handguns they carry on duty or in the
field. I wish to know what the make, model, and caliber of each weapon
used is so that I can summise which weapons are proven reliable.

(1) I don't think that this is one of the details that these services
(acting in secrecy as it is) would disclose to the public;
(2) Probably they have different weapons for different operations and
for different roles. It is hard to imagine a female agent having the
same gun as a male one; and in fact, regarding services like the
Mossad or the CIA, it could be even something developed at their own
labs (have I seen too much James Bond?)
(3) And since these are all governmental agencies, it is quite
possible that weapons would not only be chosen for quality, but also
because of bureaucratic reasons: a company that gives the best price
in a tender, guns that are manufactured in one country and not
another.
(4) Your choice of agencies is a bit peculiar. Why MI5 but not MI6? Or
Mossad but not Shin-Beth? Why Interpol, which deals mostly with
coordination between police forces?

Hi,
    Every agency use different models for their weapons, guns or
pistols due to geogreaphic reasons as many are from different
countries. But what I know is that among FBI, CIA, DEA and SWAT the
following model is most popular:-
1. LORCIN M-38 111H AIRSOFT PISTOL W/ EXTRAS 
Description: GREAT QUALITY AIRSOFT PISTOL COMES WITH EXTRA CLIP,
REMOVABLE BORE, EXTENDED BARREL AND SHOULDER HOLSTER... COMES WITH
PATCHES THAT READ CIA, FBI, DEA & SWAT. TAKES 6MM BB'S OR PAINTBALLS.
COMES IN A COLORFULL BOX
read about more AirSoft pistols as www.sharpimport.com 
2. Also M1911 .45 ACP pistol is also used as a backup by these
agencies. It is manufactured by North American Arms (NAA, Dept.
SGN,2150 South 950
East, Provo, Utah 84606; phone: 800-821-5783; fax: 801-374-9998)
very good information for you at:-
http://www.naaminis.com/news19.pdf

3. Revolver used By Interpol -
Description
Model:  Colt Single Action Army
Caliber:  .45 LC
Edition Limit:  154
Barrel Length:  4 3/4"
Decoration:  Each revolver is decorated by craftsmen specifically
commissioned by America Remembers.

I hope you are satisfied. Good luck. If need still more information
kindly write to me. Thanks

Given what I've just written about Interpol (working as a coordinatory
body, not having any authority to use weapons, at least the "Interpol
weapon" part sounds like something that some commercial body has made
up.

I seriously doubt that these agencies are using revolvers. 
Semi-automatic pistols have a larger magaazine and can be reloaded
much more quickly.

Agencies such as the CIA and sectors of the military usually issue a
certain firearm as a standard side-arm, I know they do use other
weapons as well. As for differences between female and male, they make
no distiction. A female must carry the same weapon as a male.

As for the secrecy of weapons used, it is mostely common public
knowledge. I have over time read about various weapons in use by those
such secret agencies, but I did not note what they where which is why
I would like a report. I am sure some agencies develop weapons, but
they are made by a well known company.

Phork, 
Reading various news reports is anecdotal evidence, and you cannot
conclude an official policy or to know for sure. These organisations
specialise in spreading disinformation. I've read, for example, that
according to the book "Sword of Gideon", the Mossad's assassins use a
0.22 Glock.

OK... 

And who is to tell you that what they say in this book is correct? And
even if it was, who ensures you that it is current? And even if we
assume that it is current and correct, who ensures you that the Mossad
doesn't use a variety of weapons? For different
units/operations/jobs/etc. (regarding differences in gender, I know
that for sure from a friend of mine who was a law enforcement officer
- female officers were he served were allowed to carry lighter guns.
The whole idea is effective reaction, right?)

You also haven't answered regarding your peculiar choice of
agencies/services. Why MI5 and not MI6? (because of Q?) Why Interpol?
I am pretty sure that most if not all Interpol officers do not carry
any weapons at all.

I have heard that the Ingrams is liked, the Uzi pulls up and left.
- that is raincoat stuff

Revolvers tend not to go wrong - always useful.

I vaguely remember something about 'wire, knife and hands' but it
might not be in that order.

politicalguru:

I chose MI5 because that is the UK equivalent of our CIA. I chose
Mossad because I figured it was the Isreali equivalent to our CIA. I
did not list every agency because I did not want too exhaustive of a
list. I focused my list on non-domestic agencies (of which Shin-Bet is
one) aside from American domestic agencies. I do not find my chosen
agencies peculiar.

Yes, sometimes the government chooses a weapon based on price, but
they still go through extensive trials, and from the top performers
the government makes a choice (at least in the military sector). For
example, the SIG and the Berretta went head to head in the 1980?s
military trials, but the Berretta was ultimately chosen for price.
Both where determined to be of equal reliability in the field.

I did not expect to give more answers than I have received. You assume
that the information I have run across is from news reports. What I
had in mind is that someone could make a best effort at a definitive
list. I do not expect to provide empirical evidence but rather
reputable references.

Note: MI5 is a domestic security service.

MI5 are not the equivalent of the CIA

- you mean MI6 ( alternatively known as SIS )

MI5 are like your FBI - strictly domestic.

MI6 are strictly offshore - or supposed to be.