IE8
I use IE8 for testing purposes and I am always impressed by its design and the quality of its rendering, particularly of text.
I have to ask what went wrong in later versions - why have an address bar the width of a postage stamp? Why make half-hearted attempts to copy Chrome, but persist with your 1990s style bookmarking system? Why do pages look worse then they did in earlier versions, and why so jittery?