I haven’t seen such a guide so I decided to make one to answer some of the frequently asked questions about how unboxing unusuals in TF2 crates works.
Q: What is the probability of finding an unusual while opening a crate?
A: The wiki states the probability is 1% but actual evidence has shown the the probability lies somewhere around 0.005 (0.5%) and 0.007 (0.7%). [Cite]
Q: If the probability of getting an unusual from a crate is 1%, does it mean I will get one if I open 100 crates?
A: Actually no. This is a common mistake made by many people regarding how statistics work. The chances of getting at least one unusual goes up if you have more crates and is calculated using the following formula (assuming that the probability is 1%): 1 – (1 – 0.01)^n with n being the crate count. So if you open 100 crates in row, the chances of getting at least one unusual out of them would be 63.39%. [Cite]
Q: Do old crates only give old unusual effects and new crates only give new unusual effects?
A: It is known that Robo Effects can only be obtained from RoboCrates but whether 1st generation effects (like flames) can only be obtained from old crates or not is debatable. Statistics show the people are unboxing newer crates and getting new effects more than old. Wiki says that any unusual effect can be obtained from any crate but the actual evidence shows that it might be wrong. [Cite #1] [Cite #2] [Cite #3]
Q: Can I get any unusual hat from any crate?
A: You can only get Robo Unusuals from RoboCrates but you can get all other unusual hats from any crate series. [Cite]
Q: What is the most expensive unusual hat and how many of them exist?
A: The most expensive unusual has is a Team Captain with Burning Flames effect which is worth well over 5400$ and currently only 5 of them exist. [Cite]
Q: I’ve heard people calling some unusual hats “cancer”, what does that term mean?
A: A cancer hat is a bad hat or a hat that has a very bad effect. Cancer unusual hats are hard to trade because no many people would be interested in them. They are also cheap. [Cite #1] [Cite #2]
Q: What are unusual effect/hat tiers?
A: Effect tiers is a common term among unusual trader. It means how good an effect is. There are four tiers: Low Tier, Medium Tier, High Tier, and God Tier but it’s mostly personal. Same goes for hats themselves. It also largely depends on player’s personal opinion. [Cite #1] [Cite #2] [Cite #3]
Q: What are “themed” unusual hats?
A: A themed unusual hat is a hat with a relevant effect that often adds to it’s value. [Cite]
Q: If I craft two unusual hats, will the new hat be an unusual?
A: No! Any properties that a hat might have before crafting (excluding untradeable) will be totally lost upon crafting. If you craft an unusual hat, you will get a normal hat. [Cite]
Feel free to say if you think a question should be added.