1."Compulsion."

While only the second episode of the show ever, it set the tone for the rest of the series (almost) more than the first episode did. It established the idea of the compulsion to kill, a theme that will follow the show and other killers. The clip above is only one of many tense moments in the show.

2. "It Takes a Village."

Taking place after the season six finale, the BAU team stands trial for their actions in the capture and release of Ian Doyle. Each team member takes the stand and offers their respective perspective of the events. Of all of them, Reid was the most affected by those events and the "death" of another team member. This tense moment is one of the most memorable moments of the entire show, which is how it earns its spot on this list.

3. "Our Darkest Hour," and "The Longest Night."

A two-parter. But these episodes are best viewed in quick succession with each other, instead of waiting like I was forced to when the episodes aired. Tim Curry appears as a horrifyingly creepy serial killer, who kills mothers and makes their children watch. The end of the episode "Our Darkest Hour" leaves Morgan tied up on the floor next to a dead body, while the killer gets away. ouch.

4. "Riding the Lightning." 

While investigating a serial killer couple, Gideon becomes convinced that the woman going to die for her husband's crime is innocent. This is one of the first episodes of the show that ends on a somber note, letting the true killer get away with it.

5. "Masterpiece." 

In a bizarre and terrifying subversion of Jason Alexander's usual roles, this episode features Jason Alexander as a serial killer who approaches Reid and Rossi after a lecture and challenges them to solve the murder's he's committed. Perhaps one of the eeriest episode of "Criminal Minds" to ever grace our homes.

6. "Derailed."

Elle is aboard a train when a mentally ill man begins to devolve and the situation escalates. This suspenseful episode takes place primarily in one place, the train, or directly outside of it, as the team becomes more and more in danger.

7. "No Way Out I-III."

The first recurring serial killer the team faced. Frank had three episodes dedicated to him and he tested the team in ways they have never been tested in, and probably never will be again. It revealed the darkness inside each team member and what really made them tick. It also featured one of the most shocking conclusions, a true case of a killer getting away with his crimes.

8. "Bloodlines."

This episode was criticized and rightfully so, for a racist portrayal of Romani culture. To not include it, would be ignoring yet another wonderfully suspenseful episode with a twist ending not often seen on tv. This episode, like many others on this list, stuck with me for years to come and it was a truly horrifying ending.

9. "The Fisher King I-II."

The team does their best to take a break and then immediately encounters their first season finale killer. With Elle in his clutches and Reid trying to deal with his personal issues, this episode is traumatic in violence and in the psychological.

10. "Uncanny Valley." 

A serial killer is creating dolls out of real-life women. Reid shows one of his brief moments of calculated anger when he comes face to face with who he believes is responsible for the crimes. The crimes are horrifying, and coupled with the fact that we watch one of the diabetic victims struggle to survive, along with a snappy Reid? It makes for great TV.