Hot Scientist: Calleigh is a blonde, leggy Southern girl who likes guns, Natalia is a tall, curvy Latina, Eric is half-Cuban/half-Russian, Ryan has perfectly tousled hair, and Maxine Valera is fairly cute. Also, yes, some people do find David Caruso sexy.
Jumping Off the Slippery Slope: Seems to be going this way after his near-death experience. He is noticeably more vicious and ruthless, savagely beating a suspect and even letting a man fall to his death as he begged for Horatio to help him. Granted, one man had killed a police officer and was involved in a kidnapping, and the other man was a pedophile with a long history of abducting and molesting young female beauty pageant contestants, but still.
Pedophile: '[[While hanging onto a ledge] I can change - I know it! Horatio: I doubt that. Pedophile:[His fingers starting to slip] You have to help me! Horatio:[Coldly and dispassionately, while stepping away from the man] Do I? Pedophile:[Falls to his death]''
Rabid Cop: Of the CSI leader bunch (Grissom and Taylor et al) Caine was the closest to this trope, with many cases ending with him pulling a *Click* HelloStealth Hi/Bye, shooting, beating up, or plain threatening suspects. David Caruso's gravel voice helped plenty.
Ms. Fanservice: She's prone to wearing extremely tight pants and four-inch heels, which almost always comes with the camera panning back to show her legs. She is the only other cast member apart from Horatio to appear on UK DVD sets, likely for this reason.
Southern-Fried Genius: Blonde, gorgeous Southern belle - who knows more about ballistics than the rest of the team combined.
Jerkass: Definitely had his moments, usually when speaking to women. He told one victim of harassment that it was her fault and she'd lead the guy on (she hadn't), and was rude to other female characters (excepting Alexx, Megan, Calleigh and Yelena).
Killed Off for Real: Speed is shot and killed halfway through the Season 3 premiere by security guards at a jewelry store when his gun jams thanks to negligent keeping.
Tempting Fate: When walking into a jewelry store with Horatio, Speed discusses expensive cars, disdaining them in favor of his bike. Caine mentions that he might need "something with doors" some day. Speed says he has plenty of time. He is fatally shot not five minutes later.
All Love Is Unrequited: Holds a massive torch for Boa Vista for most of the series, but she doesn't reciprocate his feelings.
Eager Rookie: When he first joined the lab, he was intent on proving himself to Horatio as much as possible. This results in him having a tendency to be competitive against his co-workers, which rubbed them off in the wrong way for a while.
Jerk with a Heart of Gold: Occasionally. He's usually called on it, though. Even so, he's proven to be a very capable cop, and extremely compassionate when he needs to be.
Last-Name Basis: Horatio calls everyone else by their first names. Ryan, tho, is always "Mr. Wolfe."
Yank the Dog's Chain: He seems to finally building up a good relationship with newcomer Sam in the final season and is on track for a Happy Ending. Then she betrays him by leaving him behind to take the blame for killing her boyfriend in the very last episode.
The Mole: When first introduced, she was actually a Mole for the FBI, reporting on the Labs activities while posing as an assistant Genetic Analyst. After getting to know and befriend all of the CSIs and seeing them all as the good cops and even better people that they are, reveals her status to Horatio, and sides with her friends, quitting her job at the FBI, and becoming a CSI herself.
Put on a Bus: Alexx leaves the morgue in Season 6 to become an ER doctor. She's occasionally appeared since then, usually when one of the team have been injured in the line of duty. She returned for a few appearances past that.
Advertised Extra: She featured prominently in ads and was supposed to co-star as a protagonist along with Caine, but the character Put on a Bus after 10 episodes in season 1.
The Mourning After: Her detective husband died on duty and she never quite got over his death. The series starts with her coming back after a six-month leave, but she quits 10 episodes later, telling Caine working there reminds her too much of her dead husband.
Chronic Evidence Retention Syndrome: She's exposed as Josh's killer in the end because Ryan finds a piece of glass stuck to her boots after the car crash. Meaning she has been wearing the same boots she had the night of the crime for several days and didn't even think to clean them up.
Dude Magnet: Walter, Eric, and Ryan are all shown to be attracted to her.
Frame-Up: She ends up being framed of tampering with evidence by her boyfriend Josh under the orders of Vogel in order to discredit Caine's CSI team.
And then attempts to pull one of her own when she murders Josh, albeit In Self Defense, and leaves Wolf, whom he'd just worked over, to take the blame for it, sending any sympathy that might have been had for her flying out the window.
Love Triangle: At first she looks to be in the center of one between Eric and Ryan. But when Eric steps down, and she and Ryan get a lot of Unresolved Sexual Tension while working together, it's revealed she already has a boyfriend.
Old Friend: She and Walter became friends back when they were working the night shift together.
Resigned in Disgrace: Narrowly Averted. After Sam accidentally ruins a vital piece of evidence by accident, she gets majorly chewed out by Boa Vista who basically orders her to quit. Sam almost does, but a pep-talk from Walter encourages her to stay and try to redeem herself by trying to find evidence another way, which she does.
Likely played straight in the series finale. It isn't shown whether she's given the choice to resign or is simply stripped of her badge and duties after being arrested for murder and attempting to frame Wolf.
Sixth Ranger Traitor: She's a new member of Caine's CSI team added in the final season and ends up being the last murderer they catch when she kills her boyfriend and leaves Ryan to take the blame.
The Lab Rat: She was a blood evidence technician in season 2. She was a fan of Quincy, M.E. as a child, influencing her to become a criminalist. She only appeared in season 2, as two years later, De Huff died from pneumonia.
The Lab Rat: He's the Audio/visual and multimedia lab technician for seasons 4 to 6, replacing Tyler.
The Resenter: After being forced to resign by Calleigh, he began to hold a personal grudge against her, and ended up leaking personal information about her online, which ended up having her kidnapped by criminals, something he didn't intend. Feeling guilty he turns himself in order to give CSI info to help catch the criminals.
Resigned in Disgrace: During season 6, he is discovered to have stolen and used a credit card that belonged to the late Tim Speedle, much to the outrage of Eric and Calleigh and Dan was forced to resign from the lab in disgrace.
What Happened to the Mouse?: Her final appearance was in the Season 7 finale, when she assists Horatio with an escaped and dying fugitive; although she was advertised as being billed for more guest appearances, her character and her son's character were dropped with no announcement instead, invoking Chuck Cunningham Syndrome.
Inspector Javert: Most if not all of his appearances involved him barging into whatever plot was happening in the episode in a constant search for Caine's team (and especially Caine) being either criminally incompetent or just plain criminal, up to and including forcing members of Caine's team to try to play mole. It was unsubtly implied that he kept doing this because of his beef with Horatio.
Internal Affairs: He's one of the MDPD's Internal Affairs officers, something he uses to constantly barge into the crime lab looking for corruption.
Put on a Bus to Hell: In his final appearance it is discovered that for all of him trying to sniff out Caine as a Dirty Cop, he was one himself, stealing vehicles impounded by the MDPD to sell off and having a District Attorney assassinated to keep it under wraps. He is arrested and never seen again.
The Resenter: Horatio made Lieutenant faster than Stetler. Stetler decided to believe that Caine accomplished this via corruption.
Amoral Attorney: He is not only very good at helping his clients but also threatening his clients to help his other clients. He's also not above framing CSI for tampering with evidence in an attempt to close down the lab.
Asshole Victim: He's kidnapped along with Sam and put into a Hostage Situation by one of his dissatisfied drug dealer clients and ends up heavily injured when Sam crashes the car.
Blackmail: He's an attorney that blackmails his own clients after he helps them hide all their dirty secrets.
Back for the Finale: He was the antagonist for one episode in season 8, building up a rivalry with CSI. He comes back for the final two episodes to be the final antagonist of the series.
Final Boss: He's the final antagonist of the series in the last two episodes, by hashing a plot to have the lab closed.
What Happened to the Mouse?: After the car crash, we see him being taken away by medics still alive, with an oxygen mask attached to his mouth, but no mention is made if he survived or if CSI ever managed to nail him down for something.
Cool Boat: Sam mentions he inherited a fancy boat that he didn't like talking about with her. Ryan finds it suspicious a man would never take his girlfriend on a ride on his fancy boat and has it investigated. It turns out He was using it to smuggle narcotics.
Love-Interest Traitor: Used his connection to Sam to gain access to the lab to implant false evidence on Vogel's orders.
The Mole: He is actually working for Vogel, and sabotages Sam's work in Vogel's behalf.
Romantic False Lead: He's introduced as Sam's boyfriend just as Ryan and her start getting close, and he seems to be better than Ryan in every way. Naturally he turns out to be in Vogel's pocket, and frames Sam for tampering with evidence to discredit the lab and free Vogel's client.
Victim of the Week: Ends up being the final victim of the show when he turns up dead in the final episode.
Would Hit a Girl: Ends up attacking Sam after she shows up shortly after he confronted and knocked out Ryan. She ends up killing him while fighting back.
Early-Bird Cameo: Is mentioned by her brother Eric back in season 1, but only makes an actual appearance in season 4.
Ill Girl: She is diagnosed with cancer and because of the painful treatments, left her weakened enough that her brother Eric had to start helping her to eat. Eventually, he resorts to bringing her marijuana to alleviate her pain and nausea but that got them both in heaps of trouble with both the FBI, CSI and drug dealers and she ironically ended up being killed by a hitman sent by the drug dealers.
Missing Parents: His father didn't know about him until he was sixteen, his mother left him with his grandmother when he was young, and his grandmother died sometime later, causing him to live in foster homes.