Cha la, inshallah.

Pretty much anything composed by Yuki Kajiura as far as favorites go.

Not necessarily a favorite, but pure nostalgia in a single song? Wings of a Boy that Killed Adolescence.

Trigun. NGE theists of a cruel angel. Tenchi Muyo. Macros plus. Any of these take me back to a time after high school before life and bills.

Anything from Cowboy Bebop.

I have two that do it for me:

This one, although it wasn't my first as couldn't easily see anime at the time, this song despite when it was made put me back in the 90s since it was for teenagers of the 2000s.

But for purely on anime, Stein;s Gate was the first anime that truly hooked me and the intro song always brings me back to the time I was so enthralled with a show.

Not an Anime, but Fate/EXTRA (and CCC) have quite good OSTs aswell, quite unique stuff there

Last Exile will always be associated, for me, with summer memories and TechTV when it was good. It's a shame how underutilized Shuntaro Okina is.

Tank! and the opening to Trigun are always some of my favorites.

Origa -- Inner Universe

.hack // SIGN -- key to the twilight

Record of Lodoss War -- Wind, Birds, and Sky

Honorable Mention: Myth-- the Fallen Lords OST Not anime, definite nostalgia bait, though.

Admittedly, I wasn't a huge anime guy as a kid. I watched some of the normie stuff (some good, some bad) that some friends who were into it watched and recommended, but it didn't have too much of a lasting impact; I don't really remember any of the songs, aside from one, which I'll get to in a second.

I only more recently (last five years or so) got back into anime, because I wanted to try it out again, and was fed up with modern Western shit. Ended up loving it, and it's most of what I watch, entertainment-wise, now. Decades ago, the main stuff I watched was normie stuff; Kenshin, Yu Yu Hakusho, FMA, Death Note, Bleach, Naruto, etc.

As for songs that stuck with me, it's actually from some anime I don't remember the name of, and haven't been able to find. Maybe someone else will recognize it. It's probably cringe; I was a kid or young teenager when I watched it, and I think it was pretty heavy in the CGI, too. Anyway, it was some dragon-centric isekai-ish (I think they could go back and forth between worlds) anime, where different groups are having power struggles over the dragons in the other world. Yup, the anime itself is almost entirely forgotten, but I can remember the opening riff to the song, kind of rock-y as I recall, around two decades later. Weird what sticks with you.

EDIT: Fuck, that brings me back. Found it! Dragon Drive. Wow.

Bravin Bad Brew hasn't left my mind in nearly 20 years despite the anime its from being literal garbage that I hate watched after I realized how bad it was going to be.

It also reminds me of a simpler time when forgettable seasonal slop wasn't just "Isekai #29" or "Moeblob #14". Like its a garbage series, but it was at least trying something. Including being a "series long love triangle" show, but with a guy and a girl and neither being false shiptease leads.

As well as Higurashi OP 1 and Naraku no Hana from the second season. Both are complete opposite of each other, as one is pure horror building and the other is pure despair and hope cycling.

But they both work so well for the series, as you show up for the cute girls doing slasher villain shit in S1 and then by S2 you are just as wanting the cycle to end as Rika does and the OP reflects that change.

Its a series that I hold close to my heart because of how many friends I watched it with hyping up each episode as they came, and because of how terrible its legacy has become because of the endless OVA seasons and becoming so "mainstream."

Rent-fucking-free: https://www.youtube.com/watch?v=xrjUj-FRorY