Alright, I can probably go longer, but here are a few manga moments I've re-read multiple times...probably too much in some cases. *sweats*
Gonna pick chapters that have been out for a while, so I'm not gonna add spoilers. If you still haven't read Rave Master...and plan to...look away!
Could pick a lot of scenes from One Piece, but Luffy's first fight with Bellamy is easily one of my favorites. Not gonna add spoilers for something that's almost 20 years old, but basically, Bellamy was this thug that kept asserting his dominance over Luffy. Pushed him around, beat him up (Luffy made a promise to avoid making a scene at the time), jeering and laughing. Finally...he commits an act of violence on someone close to the Strawhat crew, and steals something precious from them. Luffy challenges Bellamy. Bellamy still assumes Luffy is small-fry, completly ignoring recent news about Luffy's defeat of Sir Crocodile, and taunts him yet again. He charges...only for Luffy to take one of his coolest (and shortest) victories ever.

I don't talk about this manga a lot here, cuz waifu wars,, but I can't make this post without a mention of Nisekoi 199. I'm sure I've read this chatper over 30 times. It was just...such an amazing payoff, after being so attached to this fictional pairing for so long. Easily one of the best romantic build-ups I've seen...and reinforces a theme I feel strongly about: love isn't about who comes first, or who you might be the most attracted to, it's about who genuniely makes you the happiest to be around.
Also was amazing how the chapter used the title "Majikoi" or "True Love"...a nice play on the manga title.

Finally, gonna mention one of my favorite parts of Rave Master, a shounen adventure manga by the author of Fairy Tail. At the climax of one the big fights, Musica (essentially Gray) and Reina (essentially Ultear) team up to defeat one of the main villains. The two have the same type of power, and they've been something of rivals since their first encounter (with a ton of sexual tension). Reina finally reforms to help Musica, only they realize they're trapped in a situation they won't survive from. Musica is resolved to die together, which makes Reina happy...but she decides to take matters into her own hands instead.

Frick...I'm tearing up re-reading the chapter. The art style only makes it all the more tragic. And if that wasn't harsh enough, Hiro's "what-if" scenario right before her death was one of the harshest things I've read.


Buwaaaaaaaaa ;_;

*goes into exile to weep*