Bloodbath (as a result of Opeth/Katatonia)
Diabolical Masquerade (as a result of Katatonia, which was a result of Opeth)
Dissection (hard to say why, but if I hadn't heard Opeth, I wouldn't like this)
Asmegin (more a result of Vintersorg, who was a result of Blind Guardian/Opeth)
Yeah, basically Opeth is the reason that I like most of my current favorite music, because most of my current favorite music has screaming/growling. Also, their sound was very influential. Opeth also, by the way, greatly affected the music that I write.
Katatonia, October Tide, Bloodbath, Porcupine Tree, Diabolical Masquerade, Aviv Gefen, All of Dan Swano's bands, Cradle of Filth, Nevermore, Devildriver, Madder Mortem, Suffocation, Morbid Angel.... hell too many to count
apart from PT and Bloodbath etc. I wouldn't say I got into many bands because of Opeth, but they were one of the first bands I found when I started exploring extreme metal.