I don't believe in the use of <b> or <i> tags, they imply presentation, and all presentational elements should be left to the css with the exeption of a few symanic elements in the html. I would use <strong> and <em> for bold and italics if I really needed to becuase they imply meaning and screen/braile readers don't just scan over them like normal text but understand their meaning. The thing about <oblique> which means only slightly slanted, is that it doesn't imply meaning and <em> does, so I won't use that one either.
In the end, it's better to leave all presentation to the css, but if you want to imply meaning with presentation, go with <strong> or <em>. You can always change the appearance in the css later. The point of this was to say that <b> and <i> are 2 of the little gremlin tags in html and should be avoided.