I really can't say any track has changed my life significantly.
At a push I'd say maybe Shake the Disease by Depeche Mode as it really hit me at the time it came out and got me properly interested in music, as opposed to "Yeah, that's an alright tune".

A Night Like This by The Cure, as it reminds me of my first love.

I hate the Beatles, but there's a local band does a cover of Eleanor Rigby, utilising a cello, and it sends shivers down my spine every time they play it. The original could come on the radio straight afterwards, and I'd think 'meh'.

Marian by the Sisters of Mercy. Hearing it for the first time in 1987 heralded the start of my goth phase at a significant point in my life anyway.

Struggling for a fifth.

*Edit* Rue des Tempetes by the Young Gods, as it's a phenomenal tune and reminds me when I got to do work experience at the now defunct Riverside venue in Newcastle, which got me onto the guest list for any band I wanted after that. The Young Gods was the first of those.
( Davros' Granddad a voice of calm reason in a world of spastics., Wed 7 Sep 2011, 20:27, 1 reply, 15 years ago)

A band with a bunch of mates in 20 years ago
did a very grungy version of Eleanor Rigby at a Christmas gig as a one-off and then had people shouting for it at every gig for the next year...
( The Light in Chains don't touch the Pope's boner, Wed 7 Sep 2011, 20:38, Reply)