I think people cringe at the sound of this word, and to be honest it's meaning has lost all of its value over the years for its blatant misuse. I know this is going to get a lot of hate but I feel its definition is so butchered at the moment. P2W items are items that give you an edge over another endgame player. Now just because some items can give an edge doesnt mean a game is necessarily P2W.

A game that is P2W usually has 2 ways of being P2W:

• Having cash shop items that make it impossible for free users to be on equal game strength.
  

OR

• Having cash shop items that can be repeatable repurchased that have the ability to increase your characters strength.
  

Examples of Non P2W Items/Mechanics

• A monthly premium, or optional subscription. A game that offers this is highly suggesting the game is subscription modeled but is offering the game for free. You can turn on and off your premium and not be locked out of your account, and is a fairly common model.
  
• Items that boost your speed to Endgame. In most mmorpgs endgame is where you will get your BiS and will be your harder mechanics. These boost items help to skip content, but in the long run will not determine if one player will be stronger then others.
  
• Pay for convenience items. Items that can increase storage space, inventory, etc. One time purchases that make your in-game life a little easier is not game breaking.
  
• Cosmetics. Now this is considering that the cosmetics do not give additional stats. I preface this because a lot of time cosmetics give exp gain, which then would take you back to point 2.
• Mounts, items, or even weapons that a game can sell you that is clearly below BIS. Even if cash shop items sold entry level blue weapons for end game, it will not make your stronger then a F2P player that has BiS items equipped.
  

Examples of P2W Items/Mechanics

• Upgrade stones / RNG enhancers / failsafe items. Especially in games that have 10 items, and the RNG is brutal to get them up, preventing fails or increasing your RNG will make getting bis items much easier.
• In games that have Daily or Weekly lockouts for dungeons or content, items that will be able to reset that cap. This can skyrocket a whales advantage over a F2P player.
• Items such as mounts, weapons, potions, buffs that are inaccessible to F2P players that are BETTER then what is available to F2P players. A lot of times these items may be locked away in an RNG box. Rarely do we see games over pure weapons before, but o was there a time.
  
• The ability to purchase straight in game currency without cap. This is also assuming that in game currency has a value to it.
  

Items that are Borderline P2W:

• The ability to purchase straight in game currency with cap. Very subjective to how high the cap is and how much value is on that currency. If every week you can purchase say the same amount of money you can make in a day, I would say that isn't really P2W but if you can purchase every week the same amount of money you would make in that week, I would.
• In game time savers. Things such as teleports, free dungeon clears that are capped, worker speed boosts (farmville esq), these all depend on how much each mechanic plays into the main core of the game.
  
• Costumes that add stats. Depends on the stat whether it is an increase to combat or if its light radius bonus.
  

Now if a game has p2w mechanics it doesnt necessarily make it P2W don't play. There are obviously various degrees of P2W. Most of us have played a game in our lifetime where you can insert a credit card, and be stronger then a player whos been playing for months. There are other games that the p2w is gradual and over time could add up. It is ok to be specific on the levels of P2W. It is possible for games to have p2w items and the game itself not be p2w. The game really needs to break 1 of the two rules listed on top to make it p2w.

I know I probably missed a few obvious p2w mechanics, or non p2w cash shop items so I will continue to edit this list going off of the comments below.