Kyle and Yost's run on New X-Men. It's the last time that a younger X-Men actually felt like they really mattered to the direction of the books, and weren't just a disposable and interchangeable generation of wallpaper who exist solely to be tortured and killed to make the O5+ sad.
If Remender never penned his X-Force I'd be right there with you on this one. Kyle/Yost run was amazing!