I was an avid user of the tt tag for any inline code, but as HTML 5 is coming, I'll just have to settle with using kbd instead. A full list of elements you should start avoiding can be found at:
http://www.w3.org/TR/2008/WD-html5-diff-20080122/#absent-elements
One of the more alarming things we will have to learn to live without is the style attribute. This forces you to move your style information to the CSS files and put everything on the page with either a class or an attribute. But I will have to admit that the style attribute is something that I only used in quick hacks, so no real biggy there.
But there is one, I must say weird, exception: the font tag is allowed to have a style attribute. And the font tag is only allowed in "when inserted by a WYSIWYG editor due to limitations in the state of the art in user interface for these editors.". Which I think is the weirdest exception ever, but there you go.