Best wordpress theme which is free

For my main blog Blogging Park I am searching for a best free WordPress theme.I don't need any featured post slider for this theme.Two column will be fine,but this have to tabber widget.Ya a tabber widget is required for my theme.I have tried many tabber plugin for my current and previous theme but they are not running properly for all browser.Sometime one is loading and another is not.I want some smooth tabber in sidebar which could be move with mouse,while I move my mouse over the tabber title it should show the content of this tab.

Do you using any theme which has fine tabber widget?Ob course theme should be seo optimized.If you any theme for this purpose please share here,I need it very much.