The best free AJAX filter

AJAX integration workes smoothly with mostly all features. Other plugins tend to conflict with different parts of the theme (such as searches or pagination), but this one is working pretty well.
Free version has already a lot to wrok with, which is absolutely great.
The only “but” so far is the images filter: when choosing categories it would be great if it could take the featured picture of the category, instead of selecting them one by one.