If my memory serves me correctly, I believe the first I listened to was Slit Your Guts by Cryptopsy. Ultra-heavy right off the bat. Now you know why I am like I am hehe.
the first one was Godhead's Lament by Opeth...it was the clean vocals that caught me and it's been downhill (or uphill, depending on how you look at it) from there. happy times!
Cannibal Corpse's "I Will Kill You" and "Pounded Into Dust". I instantly liked the vocals, because I'd been into bands with extreme vocals (Breach, Refused, Raised Fist) for a long time.
I know I've heard bits and pieces of death metal here and there ever since I started listening to music in 1993, but the first true DM song I ever sat down and listened to was Morbid Angel's "God of the Forsaken".... although it wasn't sudden, my tastes gradually got heavier.... I was mainly a Metallica and nu-metal fan, and I just started to listen to heavier and heavier music, and it brought me where I am today....