Most of the stuff in the game is rather complex and some things are spread in multiple places. It may take a while for me to figure out and organize everything.

MARCH 25: Initial stuff on the handheld weapons. Damage, Rate of Fire, Reload times.
MARCH 26: Basics of Hip spread, the effects of Rapid Fire and Point Fire Enhance.
MARCH 28: Recoil, Laser Sight Spread, and the player's movement speed from the hip and when zoomed with various attachments.
APRIL 2: Avoided April Fools jokes, added the HMG, explosives, the damage effect of silencers, ammo capacity, special armor-piercing effects and some other stuff.
APRIL 7: Tucked the underbarrel attachments in next to the explosives. Added Suit Data image.

Coming soon: the rest of the reload times (wherever they are) and a more comprehensive chart detailing everything about the Suit and its three modes.

The Player has 120 Health.
After five seconds without taking damage, the player's health begins to regenerate. 

The Nanosuit has 100 Energy.
After one second of not using any energy draining functions, the suit will recharge 30 energy per second.
If the suit is reduced to 0 Energy, it stays disabled for three seconds before recharging.

Recoil for most weapons is low (it should be, you have a big muscle suit and future guns) and character models are rather stiff and upright.
There is not a lot of randomness when the weapon is sighted (much less with Aim Enhance), meaning accuracy and reflex are pivotal in a shootout. Aim for the head.

Weapons start off with a certain amount of Damage out to a set Distance.
After that range, the weapons in Crysis 2 lose Damage Per Meter to a Minimum Damage.
For example, the SCAR loses 0.25 damage per meter until it reaches 25 Damage.
The Single Fire mode on assault rifles has its own Damage and Range and Rate of fire.

Silencers typically have minor negative effects to go with the quietness and lack of showing a dot on the minimap.
The long range minimum damage is decreased slightly with a silencer equipped, just enough that it would take an extra body shot.
Note that the DSG-1 isn't showing a silencer - that's because it doesn't lose damage with it.

Weapons in Crysis 2 have their rates of fire measured in Rounds Per Minute.
Divide 60 by that RPM and you'll get the FireTime, or time between each shot fired.
The Rapid Fire Suit Module multiplies the rounds per minute uniquely for each weapon.

Weapons have a single Reload Time. Exception being the Marshall.
Along with the Reload time is the Fill Ammo Reload Fraction or "AddTime", the point when the ammo counter changes.

The Spread of a weapon has both a maximum and minimum, both reduced by a 0.8 multiplier when crouching.
The Point Fire Enhance Suit Module multiplies the hip spread of each weapon.
The Laser Sight Attachment reduces the hip spread of most weapons to around 3.0 and less when firing from the hip.

The functions of Recoil are mostly a mystery to me, but have some numbers anyway. Recoil is really low.
The recoil has a Maximum X and Maximum Y axis. Y for up and X for left-right.
Attack is probably the speed at which the the weapon/view is moved away from the point of aim.
Decay actively (and very rapidly) slows the Attack speed and returns to the center.
There is a small bit of Randomness to Attack that prevents the speed of the recoil from being 100% predictable.
Finally, the Aim Enhance Module multiplies the Decay of each weapon positively so that it recovers even faster.

The Mobility of a weapon is very simple.
The Base move speed multiplier of a player is that of the weapon in his hand and when not zoomed in.
When zooming in, the player's speed is decreased to the multiplier of whatever sight attachment he has on.
For example a player with a SCAR+Assault Scope will move at 98% speed and 50% when looking through the scope.
As for underbarrel attachments' negative effects to the Mobility stat in the weapon menu: no effect (unless that number is somewhere else).

When zooming in, the spread of most weapons is reduced to almost nothing.
Pistols have a bit of inaccuracy to prevent them from being just as useful at a distance, but everything else is reliably accurate out to very long ranges.

Note that the Microwave gun and both sniper rifles ignore the damage reduction of Armor Mode. Don't slow yourself down against foes wielding those.
The Hammer, Majestic and Grendel have a minor armor-piercing effect, causing Armor Mode to only reduce their damage to 80% (rather than 65%).

Power Jump gives the player 2.3x times the height of a normal jump.
It takes 20 energy to use.

The Air Stomp is a velocity-based attack. The higher you are, the more time you have to fall and the faster you'll go, naturally.
Depending on the height, the Air Stomp can deliver from a minimum of 40 damage to a maximum of 220 damage.
Similarly, the radius of the Stomp can grow from 2 meters out to 7 meters.
A simple Power Jump doesn't come close to getting enough air for more than the minimum damage. You need some elevation, a few seconds of air.

Speed (sprinting) will boost the player's forward speed to 1.8x.
Speed drains up to seven points of energy per second.

Stealth drains the player's Energy by five points when standing still.
Based on how fast the player is moving with stealth, the suit will drain up to fifteen points per second.
Stealth mode may also cause the player to take double damage while cloaked. Gotta look into this.

Armor drains 2 to 7 points of energy per second depending on the player's movement speed. His movement speed is also decreased to 80%.
Armor absorbs a percentage of damage to the Player's health. 35% of the damage is diverted to his Suit Energy.
If for example, a player with Armor is hit in the torso for 30 damage. His health takes 19 damage.

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SUIT MODULES 

Armor:
Air Stomp - Velocity based attack, more speed = more damage. Requires elevation beyond a Power Jump.
Minimum Velocity Damage = 40 out to 2 meters
Maximum Velocity Damage = 220 damage out to 7 meters
UPGRADE II - No damage from falling
UPGRADE III - 0.5x recovery time after Stomp

Proximity Alarm - Sense enemy in 30m horizontal radius (not vertical), updates every two seconds
UPGRADE II - Sensor updates every second
UPGRADE III - Sensor updates every half-second

Armor Enhance 0.5x Energy Consumption
UPGRADE II - +25% movement speed in Armor Mode
UPGRADE III - Immune to Nanosuit Jammer Bonus

Threat Tracer Highlight Bullet path within 6m
UPGRADE II - Highlight Grenades within 15m radius
UPGRADE III - Highlights Explosives within 15m radius

Nano Recharge - 2x Health regeneration
UPGRADE II - 2x Suit Recharge (60 per second)
UPGRADE III - 0.5x delay before health regeneration

Detonation Delay +2 seconds to grenade fuse when in blast radius
UPGRADE II - +2 seconds to C4 fuse when in blast radius
UPGRADE III - Fires Chaff against enemy JAW missiles

Energy Transfer - Restores 20% energy with a kill
UPGRADE II - Restores 30% energy with a kill
UPGRADE III - Restores 50% energy with a kill

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Stealth:

Stealth Enhance - Transition time to/from Stealth is halved
UPGRADE II - No shadow cast in Stealth mode
UPGRADE III - 0.5x energy drain rate in Stealth mode

Covert Ops - No Player footstep sound
UPGRADE II - Invisible to Ceph Airstrike
UPGRADE III - 2x Enemy footstep sound

Cloak Tracker - Creates particles on Cloaked enemy within 20m
UPGRADE II - Causes enemy Cloak to flicker after 7 seconds in radius
UPGRADE III - Causes enemy Cloak to flicker after 5 seconds in radius

Jammer - Scrambles the radar of enemies within a 10m range
UPGRADE II - Provides protection against enemy Radar Jammer attacks
UPGRADE III - Scrambles the radar of enemies within an 18m range

Blind Spot - Invisible to Maximum Radar
UPGRADE II - Immune to Visor Tagging
UPGRADE III - Become less visible to enemies in Nano Vision

Tracker - Tracks enemy footsteps within 25m, updates every 0.6 seconds
UPGRADE II - Footstep direction tracks
UPGRADE III - Doubled track updates, 0.3 seconds

Visor Enhance - Automatically Tag enemies when zoomed in
UPGRADE II - Enemy Flashbang grenade effect lasts 0.1x as long
UPGRADE III - Nano Vision energy drain 0.5x

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Power:

Side Pack - +1 Primary magazine
UPGRADE II - +1 grenade/explosive
UPGRADE III - +1 Attachment ammo

Weapon Pro - 0.6x Reload Time
UPGRADE II - 0.5x Aim Down Sight time
UPGRADE III - 0.4x Weapon swap time

Aim Enhance - Reduced recoil (unique to weapon)
UPGRADE II - 0.4x view shake from explosions
UPGRADE III - 1.6x movement speed when aiming down sights (versus whatever negative speed it offers)

Loadout Pro - Two Primary weapons
UPGRADE II - No Mobility loss from Attachments
UPGRADE III - 1.5x speed while carrying HMG (Versus its 0.6x speed scale)

Rapid Fire - Higher rate of fire on Primary Weapons (unique to weapon)
UPGRADE II - Higher rate of fire on Secondary Weapons (unique to weapon)
UPGRADE III - Higher rate of fire on Mounted Weapons

Point Fire Enhance - Reduces spread of primary weapons (unique to weapon)
UPGRADE II - Reduces spread of Secondary weapons (unique to weapon)
UPGRADE III - Reduces spread of Mounted weapons

Mobility Enhance 0.5x Sprint and Jump Energy cost
UPGRADE II - 0.5x Ledge grab climb time
UPGRADE III - 0.25x Fire after Sprint time

Retriever - Automatically collect Dogtags
UPGRADE II - 1 less dogtag required for support bonuses
UPGRADE III - 1.2x Support Bonus time