Sharon Agathon of Battlestar Galactica. (Athena, not Boomer.)
Jadzia Dax of Deep Space Nine.
Lisa Simpson of the Simpsons.
Olivia Benson of Law and Order: SVU.
If I had to pick just one, it would be Athena. I love the way her character is used in that show.
A second nomination for Susan Ivanova. She also gave my favorite speech ever, on television anyway.
*“Who am I? I am Susan Ivanova. Commander. Daughter of Andrei and Sophie Ivanov. I am the right hand of vengeance, and the boot that is going to kick your sorry ass all the way back to Earth, sweetheart! I am Death Incarnate, and the last living thing that you are ever going to see. God sent me.”
*
Georgia Lass and Daisy Adair (Dead Like Me)
The Doctor (all of them)
River Song
Donna Noble
Dr. Daniel Jackson (SG-1)
Dr. Nicholas Rush (Stargate Universe)
River Tam (Firefly)
Jayne Cobb (Firefly)
Sir Humphry Appleby
Jeeves
Laura Roslin (BSG)
Titus Pullo (Rome)
Q (ST:TNG)
I really like Londo Mollari, amazing character.
Mark Antony from Rome.
The last (modern day BBC tv ) Sherlock Holmes.
Inspector Morse.
Montalbano.
Peter Griffin
Preident Bartlett
Tony Soprano
Basil Fawlty
Black Adder
George Smiley-Tinker Tailor Soldier Spy (The TV series)
The correct answer is the Doctor, all of them. But, for me, especially seven and ten.
Amen.
Judge Milton C. Hardcastle and ex-con Mark McCormick (Hardcastle and McCormick)
Just for the record: I’ve decided that a poll based on the replies to this thread is too big and messy a task for me to take on. If anybody else wants to attempt such a poll, please be my guest.
Thanks for all the comments and ideas!
Michael Scofield (Wentworth Miller in Prison Break)
Not in any real order:
The Doctor (Fine Chaps - ALL of them!)
Kirk
Malcolm Reynolds
Picard (last 3 TNG seasons)
Shaun and Gus
Rose
Amy Pond
Donna
The Master (any incarnation)
Kolchek
Fox Mulder
Bert (Soap)
Cleopatra (2525)
Brisco County, Jr
Lots of “already mentioned” and one new one:
[ol]
[li]Rev. Jim Ignatowski (Taxi) [/li]
[li]Jim Rockford (The Rockford Files)[/li]
[li]Colonel Robert Hogan (Hogan’s Heroes)[/li]
[li]Chris Stevens (Northern Exposure)[/li]
[li]Claudia Donovan (Warehouse 13)[/li]
[li]Detective Arthur Dietrich (Barney Miller)[/li]
[li]Dr. Perry Cox (Scrubs)[/li][/ol]
In no particular order
Miss Landers from Leave it to Beaver
Lumpy’s father from the same
Gruber from McHale’s Navy
Emma Peel
Lt. Columbo
Angel from Rockford Files
Harry the Hat from Cheers
Diana from Waiting for God
Howard Sprague from The Andy Griffith Show
Barney Collier from Mission Impossible
I’d like to add the entire detective squad room from Barney Miller.
The excellent special about Johnny Carson last night reminded me of one of my favorite characters of all time: Art Fern, of the TeaTime Movie. A close second and third would be Carol Wayne.
Heh, in keeping with my boob fixation, you reminded me of Seven of Nine.
Dr. Richard Kimble (The Fugitive)
DCI Jane Tennison (Prime Suspect)
Mr. Teabag, Minister of Silly Walks (MPFC) 
Cheetara (Thundercats)
Optimus Prime (Transformers)
Barney Fife (seconded if he’s already been nominated).