This is an interesting topic but I'm not going into super-duper detail.
That would be way to long & to be honest, start way too many fights;
In short, I'd read & research a few top non fiction books & spec ops websites;
Richard NMI Marcinko; www.DickMarcinko.com www.Paladin-Press.com www.imfdb.org
Get a few of these popular non fiction books; First SEAL, One Perfect Op, No Heroes, Cold Zero, Bravo Two Zero, John Plaster's books about the MAC-V-SOG, James Carney's autobiography about USAF spec ops, Rogue Warrior, Red Cell, Killing Bin Laden, John Weisman's book; KBL, Dear Mom; A Sniper's Viet-Nam, Inside the Delta Force by Eric Haney(US Army Command Sgt Major, retired), The Delta Force by COL Charles Beckwith, the military/spec ops/SWAT books by Leroy Thompson, Task Force Orange(about the elite ISA), Task Force BLACK, Dick Couch(former US Navy SEAL).
There are a few fiction novels & books available too. John Weisman, David Morell(who wrote First Blood about Rambo, John J) and a few others.
As for spec ops sidearms, I'd opt for a CDR size 1911a1 .45acp from S-A, Kimber or Colt, a SIG Sauer P228/M11 9x19mm, a SIG Sauer DAK P229R in .40 or .357sig, a Beretta PX4 C 9x19mm or a "old school" Hi-Power 9mm or .40S&W. Hi-Powers from FNH or Browning and the SIG P225 9x19mm were on most hips, thieghs(SAS rigs) & underarms in the 1970s, 1980s & early 1990s.
As for spec ops "long guns" & shotguns, I'd check out the Serbu Super Shorty 12ga, www.serbufirearms.com
or the 12ga systems from www.PennArms.com
FNH P90s, HK UMPs & MP5s & M4s(Colt, HK, Stag Arms, etc) are also used often "down-range".