@GaoGaiGar:
Make them watch that. If they still don't wanna give it a chance, they might be lost causes. If they don't wanna give it a chance and they watch/read Naruto/Bleach still, start hitting them and don't you dare stop.
I totally agree with you.
I stumbled upon this music video a couple months ago, around the summer? while I was searching through the top 10% of amv.org. After watching it [for the umpteenth time] I finally decided to watch One Piece in December, and man was I hooked! Started December 1st and caught up by January 7th.
That music video is still one my favorites. 
Anyway, back to the actual thread 
What I do.. is usually beg. Haha. Or pester them until they get so annoyed they go "OKAY FINE I'LL WATCH IT IF YOU'LL JUST SHUT UP!" Yep, I'm good.
I do sometimes compromise, as well. As in "You watch One Piece and I'll watch Shakugan no Shana" and if they still dont' give in, then, well, I'll start spamming them links… upon links... upon links...
Oh, they give in. Eventually. If they don't then I'm just like "FINE, SCREW YOU. GO MISS OUT ON THE MOST AMAZING PIRATE ANIME EVER. D:<"