I've posted about this before and thought you might like an update.
I developed a Wordpress theme for mobile (cell) phones and tablets that works equally well on desktops. It's gone through a number of iterations but I'm now nearly where I want to be with it.
It is very lightweight and with a few configuration tweaks can be very fast on event the slowest connection.
The key is the full width page. Sidebars on a small screen are pretty much useless so I just got rid of them. What I've done instead is give you a onepage scroller on the homepage (people swipe up all the time) that can link to inner pages. The blog displays in one or two columns depending on the screen size. Make the container wider and your get three columns.
It's makes full use of the customizer and has a whole range of built in features: SEO, analytics, sliders, text toggles, contact forms and social media. The idea being you shouldn't need to add many, if any, plugins.
I'm using it on a number of my own and clients sites and it's going down really well. People like it because they use phones and tablets far more than they use desktops for browsing at that's why it works better than just about all the popular responsive themes.
I like it (but then again I'm biased). What do you think: http://onepage.aerin.co.uk/
And I'm quite chuffed with how this works: http://onepage.aerin...slider-overlay/
And with a few tweaks it even works nicely with woo: http://bobby.testblog.co.uk/