When he first made his appearance at the beginning of the Thriller Bark arc, it seemed as though Brook was simply going to be a comic-relief sort of character who might just make for a humorous musician on the Sunny, but during his time as a Strawhat, he has shown that he is actually a very layered and sympathetic member of the crew with there being much more to him than meets the eye.
Despite being very knowledgeable about the Yonko very early on in the story, Brook's also demonstrated on several occasions that he can also hold his own in a fight, especially post-timeskip where he's reached some incredible feats in combat. All of this has resulted in some extremely memorable moments throughout the series featuring everyone's favorite skeletal musician which have truly shown his character in the best light.
10 Becoming The Soul King
During the time skip period, while Luffy was hard at work honing his Haki with Rayleigh and the other Strawhats where preparing for the journey ahead, Brook was being labeled as "Satan" by the members of the Nakamura Island. This did end up working in his favor though when he is kidnapped by the Longarm Tribe who decide to keep Brook captive as their muse.
All of a sudden, Brook had a flock of new fans proclaiming him as the "Soul King", granting him a much deeper understanding of the soul which would enhance his abilities, ready for the eventual reunion with Luffy and the crew.
9 Saving Robin And Franky From Tararan
The first time we really get a peek at Brook's combat style was during Thriller Bark when he annihilated the General Zombie Tararan just as it was about to stomp on Franky and Robin, but what was even more surprising was that Brook actually managed to kill the zombie spider by returning its soul to its rightful owner.
This was the moment where it became clear that Brook knew a lot more than his quirky and hardheaded exterior was letting on, and his quick hack-and-slash style confirmed that he would be the second swordsman to enter the crew.
8 Defeating Zeo
Fans kept a very close eye on the Strawhats during the Fishman Island arc whenever it looked like they were about to get into a fight, and the reason for that was because it was the first time each of them could demonstrate their newfound abilities and powers that they had retrieved during the timeskip.
While Zoro was definitely still the strongest swordsman on the crew, it's fair to say fans were still extremely surprised at Brook's new skills as he immediately stepped out of Neo's circular attack, slicing him in half with his chilling Glancing Song technique. The ice motif introduced in this fight also became a much bigger part of his overall fighting style from then onwards.
7 Calling Big Mon "Young Lady"
It's easy to forget just how old Brook actually is due to his rather childish behavior, but he reminded fans in a very surprising and bold way when he called Big Mom a "young woman" to her face during his speech about rescuing Sanji which itself was an incredibly rare moment of Brook demonstrating the raw emotion that lay behind the smiles and jokes.
As flames rage in the background, and Brook is about to go toe-to-toe with one of the most powerful beings in One Piece, this was most definitely seen as a very risky comment that could very well have sealed his fate for good.
6 Wiping Out Black Maria's Subordinates
Because of the way Oda likes to pace the story, we rarely ever see the other Strawhwats other than Luffy training, with a lot of it happening off-screen, which is also usually the case for Brook. However, this does also result in some incredibly surprising and impressive moments such as when Brook completely decimated all of Black Maria's henchman in a single attack.
While trying to defend Robin who was taking on the Tobiroppo, Brook was tasked with holding back the small group of henchmen running to Black Maria's aid, but rather than engaging in combat, he simply makes a narrow passageway between two giant ice blocks and proceeded to collapse the ice, lining up single swift attack to defeat the whole group in one.
5 Entering His Spirit Form
Considering he was supposed to be the ghostly undead member of the crew with an affinity for souls, it was peculiar that Brook didn't really have any abilities that reflected this before the time skip, but when he, Zoro, and Usopp are captured in Fishman Island, he demonstrates a brand-new ability that shocked both the Strawhats and the fans.
Brook leaves his body, entering his "spirit form" to help them escape and prepare for the upcoming battle for Fishman Island. It's a shame that Brook doesn't utilize this ability more often after this point in the story, but it definitely caught everyone off guard when it happened and proved that Brook had been learning a lot during his time with the Longarm Tribe.
4 "I'm Glad To Be Alive"
Brook certainly hasn't had an easy life as a pirate, so when the nightmare finally ended on Thriller Bark and Moria were defeated once and for all, Brook takes a moment to reflect on how Luffy's arrival had completely turned his life around. Not only did he find out that his long-lost friend Laboon was still alive, he also reunited with his shadow, and found an entirely new group of friends who accepted him with open arms.
As Brook breaks down crying while playing Bink's Sake on the piano, it results in an incredibly heartbreaking moment where he finally realizes that he will never have to be lonely again after accepting a spot on the Strawhat crew.
3 Smashing Mother Caramel's Picture
Brook has somewhat of a humorous relationship with Big Mom during the Whole Cake Island arc, with him either being best friends with the devastating Yonko, or her sworn enemy at other times. The latter was certainly the case when he smashed Mother Caramel's picture to pieces while disguised as one of the Luffy duplicates infiltrating the wedding ceremony.
This was a genius, albeit very risky way of getting Big Mom to scream and enter a state of confusion, giving Luffy and Bege's forces enough time to harm her with their rockets, which was a plan that ended up failing miserably. Nonetheless, it was a moment that demonstrated just how fearless Brook is as a character, committing an act that many believed was the biggest taboo in all of Whole Cake Island.
2 Revealing His Backstory
One Piece is a series known for its incredibly tragic and unfortunate backstories, but undoubtedly one of the saddest and most gutwrenching is Brook's tale of how his entire crew died one by one from disease and poison, with only him being left to play the crew's favorite song, Bink's Sake, all alone on his ship.
When Brook himself died, he was revived thanks to the power of the Revive-Revive Fruit, but this only made him feel isolated and lost in the world, that is until Luffy and the gang showed up. It’s incredibly hard not to feel sympathetic for Brook after seeing how his friends left him, and it makes his quest to see Laboon again all the more emotional.
1 Stealing A Road Poneglyph
Acquiring a copy of Big Mom's Road Poneglyph was an ambitious goal to say the least, and while all others failed to even get close, it was actually Brook who stored a copy in his skull, revealing it to Nami, Chopper, Carrot, and Pedro after they escaped from the threat of Big Mom's guards. In fact, he even admits to using the others as bait so that he could retrieve it, showing that he was a step ahead the entire time.
The nonchalant tone Brook has when revealing the Poneglyph really sums up his character as the chilled and relaxed companion who manages to surprise everyone when they least expect it and is arguably one of the biggest achievements by any of the Strawhats in the entire series so far.