Jared Followill

At 0:46 their guitar tech is shown demonstrating the Boss ME-50 for the beginning riff of Closer.

Jared Followill's Boss ME-50 Guitar Multiple Effects Pedal can be seen around 0:32 in this video of his bass gear rundown. Jared's guitar tech then goes on to demonstrate how the opening bass riff of the song Closer is achieved, by using the pedal of the ME-50 to pitch the sound up a full octave. There is a bass version, the ME-50B, however Jared Followill is set up to use the ME-50 as his tech states.

Talking about Kings of Leon’s album "Mechanical Bull," the official TC Electronic site says Jared "...Recently ... added the 'Hall of Fame Reverb' to his pedal board." Original source link here.

Listed as one of the pedals used by Jared Followill on the TC Electronic site. Original source found here.

Listed on his TC Electronic artist profile page. Quote from the article: "Seeing how reverbs were Jared’s most used effect type for the recording of “Mechanical Bull”, TC effects are now a key element in Kings of Leon’s live sound. What is more, the BH250 bass amp and Flashback x4 are always backstage with Jared before shows." Original source found here.

In this video, Jared Followill's guitar/bass tech says that Jared "runs a bunch of effects, you can tell we've run everything through a GCX Ground Control Switcher," which refers to the Voodoo Lab GCX Guitar Audio Switcher (0:18 into the video).