Not a TON of method to the madness at the moment, but I'm going for a semi-chronological order and it should be noted AvP2 was supposed to take place 50 years after Alien 3. So the AvP2 stuff is near the end in most cases but everything else will be a bit slapdash...
OK, first up is weapons!
*As a reminder, these weapons are
generally NOT including the "Big 3" (Pulse Rifles, Smart Guns, and flamethrowers) and their variants, but some interesting ones have received notations. I hope to address the variants more completely later (which would also include community made variants).
Little Known "Aliens" actual weaponsMost here already know this, but maybe some newer/younger folk arent aware, these weapons ARE in the movie.
-SA80 (a whole rack of SA80s & M16s are in the armory. They are visible pre-hypersleep chambers opening and during Frost's weapons check)

-"Boom sticks" (I actually dont know their real or fictional name) These are harder to spot, but near the end as Ripley escapes the collapsing landing pad and climbs into the Drop Ship before Bishop speed away, she sprints past a whole rack of these on her way to her seat to brace for detonation.

Tech Manual-M4A3 Service Pistol (Vasquez's S&W M39 is often mistaken for this weapon, but they are not the same)

-VP70 (no pic here, but its clearly a VP70 and they call it a VP-70)
-M42A Scoped Rifle

-M83A2 SADAR

-M112 HIMAT Anti-tank mortar

-M5 bounding mine

-M5 Rocket Propelled Grenade launcher

-M78 Phased Plasma Infantry Gun (“PIG”)
Aliens: Colonial Marines -Armat M4A3 Service Pistol

-Armat M4RA Battle Rifle

-Armat M37A2 Shotgun

-WY Mk221 Tactical Shogtun

-Armat M39 Sub machine gun

-M5 Rocket Propelled Grenade Launcher *Note same name, but different design as Tech manual

(Profile shot needed. VERY different look despite same name as RPG in tech manual)
-WY 88 MOD4 Combat Pistol (a VP70, but not called that by name unlike the Tech manual)

-WY NSG 23 Assault Rifle

-XM99A Plasma Pulse Rifle (better pic needed)

-”Sonic Electronic Ball breakers” (…ugh…,not pictured. Similar to the M5 ‘bounding mine’ in tech manual that launches near waist high before detonating, but it uses electricity rather than traditional explosives).
-S.H.A.R.P stick… (...double ugh….not pictured. exploding harpoon gun).
Aliens Vs. Predator 2010 (aka AvP3, aka "the Rebellion one")
In addition to the “big 3” (which its interesting to note they call the Pulse the “M41
A2”, and the Smartgun the “M59B”…implying they are newer replacement weapons) we are introduced to:
-VP78 Pistol (looks like a Berretta, but based on name, it implies it the newer replacement of the VP70)
-M42C scoped rifle (presumably replacement of M42A in tech manual)
-M260B Flame thrower (presumably newer replacement of M240 flame thrower)
-ZX-76 Shotgun
AvP2 (sierra)
MissMorph’s compilation image of all AvP2 weapons shows, in addition to the ‘big 3’, the following marine weapons:
-M4A4 pistol, grenade launcher, Sniper rifle (Scoped Rifle), minigun, SADAR, and “Skeeter” rocket launcher
-Here are is a nice reference to see how the weapons compare (in appearance) between AvP1 and AvP2 .
http://www.angelfire.com/pro/avp/marine.html-The pistol is called the “M4A4 pistol”, presumably making it the newer version of M4A3 listed in tech manual.

-For some more cool info on the M90A3 ‘minigun’ see Russ Krook’s thread (includes some fan fiction and more pics).
viewtopic.php?f=3&t=9418&hilit=m90a3-The “Exo Suit” (basically a weaponized power loader)

For a really great page with lots of "real world inspiration" comparison pics, see this link
http://www.imfdb.org/wiki/Aliens_vs._Predator_2Better pictures and comic/graphic novel weapons welcome! Tomorrow I will try and tackle the human 'bad guy' forces and maaaybe variant aliens.