Pop star Ke$ha stars in her docu-series "Ke$ha: My Crazy Beautiful Life" on MTV. (MTV/Courtesy of MTV )

The Glades goes gun crazy when a man who calls himself “The Mayor” brings in illegal artillery on “Arrow” (CW at 8 p.m.). Oliver is forced to sponsor a fundraiser, “Cash for Guns,” in an effort to rid the city of weapons, but the Mayor and his gang crash the event and injure Sin, which starts a war within the community.

There are ritualistic-type murders going on in Utah and the “Criminal Minds” (CBS at 9) crew is on the case. To further TV’s witch fascination, the Behavioral Analysis Unit’s probe into the small town reveals that the killer may have a fascination with the Salem trials.

RETURNING SHOW: The extremely frugal and often baffling “Extreme Cheapskates” (TLC at 9) is back for a second season with a couple who share showering and a toothbrush to cut costs. We then meet a woman who devotes only a third of her family’s combined income to their living expenses.

The long-standing truce between the Coven and the Voodoo is threatened on “American Horror Story: Coven” (FX at 10) when the truth comes out about Fiona’s vengeance for Madison. The Council of Witchcraft visits the school with allegations against several of its members.

Rayna grants Robin Roberts an exclusive interview on “Nashville” (ABC at 10), while Teddy announces to the media his recent engagement. Elsewhere, Juliette crosses paths with Charlie Wentworth and Scarlett asks Avery for advice.

RETURNING SHOW: Get your disbelieving faces ready for the series opener of “Hoarding: Buried Alive” (TLC at 10). Giant, toppling piles of clutter fill Jessica’s apartment, who in tandem with her mother, Dale, has filled their entire home with stuff that endangers their safety.

“Ke$ha: My Crazy Beautiful Life”(MTV at 10:30) takes us inside the world of the scandalous multi-platinum recording artist as she faces her biggest personal and professional challenges. Shot over the course of two years, the docu-series provides unprecedented access and attempts to show a side of Ke$ha that fans don’t already know.

Actor Will Arnett comes to the “Late Show With David Letterman” (CBS at 11:35), with musical guest the Avett Brothers.

Reality star Kim Kardashian and actress Abigail Breslin join “The Tonight Show With Jay Leno” (NBC at 11:35), along with musical guest Two Door Cinema Club.

Actor Ben Kingsley and comedian Rob Delaney visit “Jimmy Kimmel Live” (ABC at 11:35), with a musical performance by No No No.

— Rachel Lubitz