Here's my list of favorite characters! I'm going to put two for each.
CSI: Crime Scene Investigation
-Sara Grissom (previously Sara Sidle, but she married Gil Grissom, who no longer is in the show.) Unfortunately, Sara is not a permanent part of the show anymore.
-Greg Sanders: He's the youngest out of all of them, I believe, and is hilarious!! Although naive at times.
CSI: Miami
-Horatio Caine: Of course! The man himself! Smart, quick-witted, clever, and intimidating, he also has gone through a lot of drama in his life but is a strong man. Man, I sound cheesy right now. Oh, and his one liners are cool. If I didn't pick Horatio, I'd pick Delko.
-Calleigh Dusenque (sp?): She's just awesome in her own way.
CSI: NY
-Hmm... I don't get too attached to these ones. Probably... ugh... whatshername... that woman who goes with Mac Taylor everywhere... she's played by Sela Ward.
-Flack or whatever his name is. The guy with the New York accent, naturally.

My favorite character is the one played by Gary Sinise. Mack I think? I haven't watched CSI in so long.