A little unconventional and not really shreddy, but for me it was the music from Sonic Adventure, particularly “Open Your Heart” and the character select jingle.
I was probably 7 at the time, and had gotten an N64 the year before. I went to spend some time with my uncle and he had a big screen TV, a proper sound system, and this playing though it. Going from Super Mario 64 to this was…incredible. And try as I might I haven’t found anything else that sounds quite like this. Jun Senoue has some beautifully smooth playing.
A while after that someone made me an “Intro to Metal and Punk” mix tape with Black Sabbath, Armageddon, UFO, Iron Maiden, Metallica (Kill 'Em All), Megadeth (Rust in Peace), Testament, Sepultura, The Sex Pistols, and X-Ray Specs. Possibly also Siouxsie Sioux, can’t remember.
Guitar Hero 2 was the final nudge, but at that point I didn’t have enough time to play or enough money for equipment, so I waited through high school and college, saved up, and bought my first electric.