BusinessTime is clean, responsive HTML5 theme by NeptuneThemes that limits images and relies on CSS and CSS3 techniques for much of it's style. It has five levels of responsiveness:
1200px (Modern desktops and laptops)
960px (Tablet landscape)
768px (Tablet portrait)
420px (Phone landscape)
300px (Phone portrait)
At the lowest levels, all menus are converted and combined into a drop down form.
It's built on a 12 column grid, and theme settings allow you to adjust the widths of four preface and postscript regions by selecting grid units (similar to the Omega theme). In addition, the width of the two sidebars as customizable, as is their position: you can have them both appear first, split them left and right, or have both pushed to the right.
There's an animated Superfish dropdown included, and Formalize and Normalize are used to conform the browsers.
The demo uses the Flexslider module for it's slideshow with it's own default styling.