This guide is hella old. Literally over 2 years old.
Also it's semi bad advice. Stop giving me awards.
Anyone interested in expanding/updating this guide, hmu.
Also I know some of those game modes were made, which is kind of good because I added that section for future proofing.

Now, I am a bit hesitant to explain how to aim in Pavlov, because it is just like in real life. I have ♥♥♥♥♥♥ scary good at aiming a shotgun, and as soon as I see them, I can pull the trigger and get a headshot. I got to thinking, and found out how to train your muscles to aim.

Visual scanning with your weapon:
When you look around the map, you should be holding your gun to wherever you are looking. This doesn't have to be ADS, but you should just point your hand wherever you are looking like you are using a laser pointer. As soon as you see something, you can shoot it.
Muscle memory training: Load up a deathmatch game, maybe even an aim training map, and get to shooting. Work on if for about 3 games, or until you can headshot without looking through the gun. Once you can get this down, you can join into a search and destroy, and check your corners using the before mentioned visual sweep.
Corner checking:
If you have to go from A to B (literally) and you aren't sure where everyone is, take this step: use more than one gun. Sometimes there are spots in which multiple hiding spots can shield people, but you cannot check all of the spots. Use a two handed visual sweep, or with a two handed weapon, point to the spot that you are not looking at. That is a quick and dirty corner check. Someone is bound to shoot you if you aren't even looking at them, let alone pointing your gun at them. So here is the slower version. You know how in battlefield and PUBG, you can peek around corners? Same for real life. If you don't want to expose yourself, just peek your head around the corner and hide. If you see someone, you can use the second video game move, blind firing. You feel like a baller when you get this right and to other people look like a hacker.
EXPLOIT TIME:
I found a glitch I have been keeping to myself: double scope television. If you buy two scoped weapons, one hand will do the scoping, and the other weapon will have a mirrored image. You can look around corners using one hand and shoot with the other, without ever peeking your head.
@davevillz if you hear this and fix it, keep it in the game as one of those fiber optic cameras the SWAT or FBI use.

Some weapons are bad, and some weapons are good, and there isn't much in between.
Competitive weapons: AWP, AK, M4, DEAGLE, AUTO SHOTTY
these weapons aren't necessarily better than any other weapon, but people grow accustomed to force buying when they have money, and eco-ing when they don't. These weapons are the best, and when up against someone who doesn't have one, the odds are stacked against them.
The good weapons (the unsung heros):
M249 Bullets for days. Good cover fire, and a large price. I bet people don't buy it because they don't know how to reload.
Five seven: Good recoil, good clip size, good damage, good price. Technically it isn't the best pistol, but it is a good pistol to akimbo.
Nova: This is the weapon I was talking about when I said I get headshots. The pump action feels good and in the moment. I only wish you could pump it with one hand like in the movies.
Carbine: Bolt action sniper rifle without a scope. You can still buy a scope, and it makes you feel like an american sniper. Badass / 10

The in between (The old reliable):
SMGs: it is a strange middle ground between pistol, shotgun, and rifle. The spread is good, and the ammo is plenty. Good for bad economy teams or the round after pistol round. Honestly, why buy an SMG when the shotguns go for around the same price? The only reason I can see this is if you wanted to play the quiet game and attach a silencer.
The glock: it's ok if you have another hand to stabilize it.
The sawed off. It is a close quarters beast, but with only 4 bullets, you could have 3D printed a gun as good as this. Reloading is satisfying tho, so I hope davevillz makes a full double barreled shotgun. Feel like he won't because I think he only uses guns from the free unreal engine weapons asset pack. (Exposed)
Knife: flies in a straight line, that's all I have to say.

The bad:
Revolver: Takes ages to reload, around the same damage as the deagle. I would love it if the dev (@davevillz ) put in moon clips or something, and let you spin the gun or wheel. EDIT: They added it a while ago, kind of. If you close your revolver, it will automatically spin.
The auto: This game made the most OP game from CS:GO, into the worst sniper. I rather buy 3 carbines than an auto. The scope is so bad, the real strategy is to hip fire. Really a close quarters sniper rifle, high damage, semi auto.
The gun you start out with, the M1911. IRL, this gun kicks ass. Every other game seems to get this, but not this game. You shoot someone in the legs, arm, or chest? It is as if you never shot them in the first place. It's ok if you are planning to metal gear around the place, but make sure to buy the $250 silencer, or there is literally no upside. Just ask for a drop or kill a bot.
Drum mag shotgun: If you use it, I hate you.

Also could we get a zeus x27 or a baseball bat or something? I want another melee weapon.

S&D (Bomb defusal):
If you don't know how to play this, you would suck at keep talking and nobody explodes. The numbers are in the top right corner, you press that button, then the next until you have 4 digits. Disarming is a bit harder. You need to do ~8 digits, which, if you are lucky or skilled, will take you 6 seconds. Better thing to do is to get a defuse kit. The way you cut the wires is by holding the clippers over the wire and pressing on the trigger. Be careful, the clippers take a half second for each wire to press down. That is a clever way to balance out the clippers, but I want to hear what he has to say about me buying 2 defuse kits.
Deathmatch: Kill till the time runs out.
Team deathmatch: protect your buddies by stealing their kills.
Gungame: Each or every couple of kills will grant you a new gun to kill with. The final gun is a knife.

Community game modes:
Trouble in Terrorist Town: 1/10 people are detectives. 2-3/10 people are traitors. The traitors have to kill the innocent terrorists. The detective(s) have to find out who the traitors are by using their buy menu/body testing/prowess. The most useful thing about being the detective is that you, and everyone else know you are the detective. While it feels good to get the weight of suspicion lifted off of your shoulder, you will naturally be a higher value target. There is normally a tester room in the map, where you can go to get tested. This just allows for more strategy. (Do I make the innocent go in the tester while I plant a bomb? Do I go into the tester, just to be safe from a grenade my buddy threw?) These testers come in all shapes and sizes, some requiring buddies. With this tester, three people go in, if 1-2 are traitors, the light will be red. If all are traitors, the light will be green. The bomb is an optional part of the game. You can arm it for however many seconds you want. In GMod, at least, if you put the timer for longer, the beeps it would make would be few and far between, as well as quieter.
Murder: Honestly all I know is that there is a murderer and a good guy with a gun. Strategies vary from map to map.
Battle Royale: 50 people drop onto a map. You have to find weapons to kill each other with. Last one on the map wins.
Zombies: Survive for as long as possible. Occasionally, the game will let you play as a zombie after you die.
Jail break: Prisoners try to escape, and guards control what they can and cannot do.

Hopefully some people find out how to make these gamemodes:
The Hidden: One guy has unlimited knives (or a silenced m1911. It does less damage), and is invisible. The rest of the server has galils with RDS.
Limited ammo option: When you buy a gun, ammo clips are automatically put on your body.
Payload/control point/CTF.
Juggernaut: One guy is an absolute unit. Massive health. M249. If he stays the juggernaut for 30 seconds he wins.
Firefight: Co op base defense. People have made maps for this type of thing I think.
Minigames: Varies from map to map.
Infected: 2 people are infected, and have to kill to infect more people
Death run: (I almost forgot about this game mode. I love it) People are on a wipeout styled course. The guards have to trigger traps to stop the prisoners from escaping. At the end, the prisoner can challenge the guard to a competition, or in some cases they just give the prisoner a OP weapon and let him shoot the guard.
The ship: Each person has a quarry to kill, but nobody knows who that is, until you ask around. Security cameras would be hard to program, so a quarry based deathmatch would be enough.
Hide and go seek: One person has a knife while everyone else runs to hide.
Sub Rosa: The creator of sub rosa (@CrypricSea I think) sort of confirmed that it won't be coming to VR. Basically, two companies have to cooperate to get money to buy stocks/weapons. However, the teams can double cross each other, giving the alive team extra money and rendering the dead team at a net loss. Strangely, the guns are sort of a precautionary measure to keep the deal going smoothly.
Smash: IDK how you would make this, but there are rocks that break parts of the platform you are on.
Slope: rocks slide down a slope you have to climb.
Pirate ship wars: (Blackwake / naval battles before they sold out) command a ship and shoot at another ship. Ships with damage sink.
Grenade ski ball.
Shooting range darts.
Titanfall.
Cops and robbers.
Cowboys and indians: (basically cops and robbers on a train)
Turn based shooting.
(If the baseball bat becomes a weapon) home run derby.
Top down arcade minigame.
Super Monkey Ball
Trivia
Clay shooting.
Fencing (knives, no moving allowed)
Pistol dueling.

Hopefully I have future proofed my guide.