Ambiguous Ending: Most episodes imply that once the angels have done their work, that assignment is finished. However, some episodes seem to leave loose ends. Sometimes, future episodes clear these up (ex.: Season 2's "The Feather" was an extension of "Fear Not," the Christmas episode from Season 1). But some are left hanging. For example:
Did Carla Robinson have to return to prison after realizing her guilt in "True Confessions", even though the court had formally declared her innocent?
Awesome Moments: The Christmas Miracle of the episode with Randy Travis and his disabled brother features Monica taking the place of the resident Littlest Cancer Patient as the angel in the church Christmas play, to fulfill The Promise that her teddy bear would get to fly. The mechanism is weak and the rope old and can't hold her weight, so it breaks—and so to keep from having to 'kill' her current human form, Monica is forced to reveal herself in all her angelic glory. The end result, with the animals in the stable and the gifts of the Magi (and their costumes) becoming real, and the less-than-stellar organ and choir being augmented into full heavenly glory as they perform the Alleluia Chorus from Handel's "Messiah", is truly stunning. (The teddy bear? It turns into the iconic dove.)
Complete Monster: Satan is the source of all evil and darkness, and seeks to tempt those into falling to sin. In season 2's "In the Name of God," he attempted to incited a race war while disguised as an authority figure, causing one angel, Tess, to lose her powers and be temporarily replaced. In season 7's "Netherlands," he attempted to corrupt a weakened Monica after a terrorist bombing killed dozens of people. In the series finale, he causes an explosion within a school, killing dozens of children and several teachers. He then accuses an innocent man named Zack (really God in disguise) of being the culprit. Arrogant and prideful, Satan desired nothing less but to destroy everything that God valued out of petty spite.
Deader Than Disco: This was a Top 10 show at the height of its run, even outdrawing The Simpsons in its Sunday night time slot, but after a schedule switch to Saturdays, the ratings plummeted, and many former fans now pretend it never existed. Or that they only watched ironically.
Monica's crisis of faith and temptation by Satan in "Netherlands" is the direct result of her witnessing a building being destroyed by a bomb, killing many. It aired May 6, 2001, and a repeat had to be pulled from CBS's schedule in the wake of 9/11 later that year.
John Dye, who played Andrew — an angel of death — from the second season onward, died in January 2011 of a heart attack. Out of the four main protagonists, he was the first and (thus far) only to go.note And, ironically enough, the youngest cast member of the quartet.
The first season of the show had an angel of death named Adam as a recurring character. He was played by Charles Rocket, who committed suicide in 2005.
Season 3 had an episode "Sins of the Father," where a character played by Robert Ri'Chard has, and takes, the chance to walk away from gang life after being tempted to kill a man. Four seasons later, Ri'Chard would star in an episode where his character kills a former mentor and is sent to prison for at least 25 years.
The 1998 episode, "The Trigger", features a family torn apart when a woman's sister kills the former's abusive husband and every member, including the couple's young son, display a wide array of emotions (the boy felt a great deal of anger over his Dad's death and hatred towards his mother and is last seen in the episode walking off-screen, still angry and surprisingly this was not resolved by the episode's end.) Eight years after the episode aired, the actor who played the boy, Joseph Pichler, went missing and has yet to be found.
One episode involved a woman trying to pass the physical trials for the military, and struggling with climbing a certain wall. The sarge in charge tells her she doesn't have to climb it, after failing to drive her off. At the last second, she realizes it's a trick and then climbs it anyway. As of 2015, women in the US military still have much lower physical standards than men.
Nightmare Fuel: A surprising amount of it. "The Man Upstairs", "Into the Light", and "The Occupant" come to mind.
Gregory, just Gregory. Unlike the shows fairly tame portrayal of Satan he was like a demon from a horror movie complete with demonic growls as he was exorcised.
"Redeeming Love" from season four has some of this. The episode involves Monica helping a crack addict named Lydia, and viewers are spared nothing when it comes to the withdrawal process. In-universe, Lydia has some nightmares of her own, one involving a giant spider.
Any episode involving explosions, guns, or other violence can be this depending on the seriousness of the situation. The same is true for episodes involving mass or graphic death. Season two's "Dear God," involving the Holocaust, and season four's "The Spirit of Liberty Moon," involving the persecution of Chinese dissidents, get special mention.
What an Idiot: You DID have to feel bad for the victim (as well as his parents) in the episode "The Peacemaker", but at the same time, you realize he was also this in the end. A teenage boy with a troubled past involving drug abuse is graduating from high school and is also dealing with his parents' failing marriage. So, the kid one day is in a bank when it is robbed at gunpoint. One of the robbers tells him to give him the money (which even Andrew urges the boy to do so that he would not be needed), but he refuses, saying that he needs it for an important reason. He is shot because of this and dies. So while the parents are blaming each other and themselves for his death and fearful he needed the money to buy drugs, Andrew and an independent filmmaker come to them one night and gives them what he needed the money for; to pay him off for a tape made for them to remind them of him as he's away at college and fonder memories of them in an attempt to stay together. It worked. However, you have to wonder why he gave up his life just to keep his folks together when he could have gotten the money some other way (maybe through the Angels' help, perhaps?), gave them the tape and live.