As my friend DC mentioned the stoner rock scene in UK is pretty badass too, so, I am going to represent some stoner rock from the UK and Japan. Here are some videos that you should check out, click on the band and it will take you to the youtube:
Church of Misery (Japan) - Most of their songs about serial killers, but the music is heavy, riffy, bluesy, and you wouldn't know that they were from Japan!
Orange Goblin (UK) - RIP. I was fortunate enough to see these guys on a reunion tour twice this year, and they are one of the best stoner rock bands around. Killer riffs, beer-drinking, and hell-raising rock n roll!
Eternal Elysium (Japan) - Riffs, riffs, and riffs. The album Spiritualized D has some of the heaviest rock riffs known to man, and this album to me, just kills it.
Black Sabbath (UK) - It would be wrong not to have the innovators of the genre to be listed on here. Some of you heard the radio hits, but you should really look into the deep cuts. Iommi knows how to write riffs, check this one out, this was in the early 1970s!