I originally wanted to play guitar, because ever since I liked music I was a guitar fan first. When I first saw a bass, I WAS INSTANTLY HOOKED. It was just SO BADASS; I originally called it, when I was a kid, the "big long guitar with the four fat strings.
And those lows....I just loved that rumble of the B.
From this point on, I looked in some of my favorite bands to see how bass made an impact. I know these guys have much less talents than some jazz and funk players than influenced other people on this board. But these players did it for me.
I didn't think punk had any bass whatsoever (especially the Sex Pistols after Sid Vicious joined), but after listening to Rancid, Matt Freeman (althought I personally didn't like his TONE per se) DROVE VIRTUALLY EVERY Rancid song. He is the definition of cutting through to me, and when I heard his sound, and realized bass players don't have to go virtually unheard, I had made up my mind: I WAS GOING TO PLAY THIS INSTRUMENT, NOT GUITAR. Some of Freeman's lines just ROAR.
The real "tone" epiphany came when I listened to Rage Against the Machine. To this day, I love the sound Timmy C got out of his MIA J's and Musicman Stingrays (he didn't use Stingrays often.) I love his tone; warm, yet it cuts through like crazy and has more than enough attack for me. Since I am not a big fan of the "Buttload of Treble and some Bass" tone of Matt Freeman, Timmy C was the first tone monster.
I also liked Eric Wilson's, formerly of Sublime, tone; but it has more deep bass than I would personally use.
Did I mention Cliff Burton? THE INFLUENCE ON PLAYING METAL BASS. If it wasn't for Burton, I wouldn't even have considered playing bass in a Slayer-type setting. Now, I have my own ideas for a metal bass (Stainless strings, neck through, tuned BEAD).
It's a beautiful instrument, I have never looked back. People often wonder why I switched. I personally think the bass guitar was calling me from the time I was born; I just didn't hear it, and I couldn't answer the call until I knew it was there.

= forever.