Remington Steele.
A great show back in the 80’s. Many tears were shed when it was cancelled.
Thomas Magnum would be a close second.
David Addison from Moonlighting would be third.
They just don’t make detective shows like they use to. 
Another vote for Columbo…the 70’s Columbo especially.
Lenny Briscoe.
Either Jim Rockford or Wojo.
Another vote for Monk. Tony Shalhoub is perfect. It’s the only TV show I tape while working nights.
I cant remember his name but the Guy who plays the main Detective on Law & Order: Ciminal Intent.
Remington Steele, of COURSE.
Best damn detective show ever. It had romance, mystery, drama, humor, and you could cut the sexual tension with a knife. I’ve devoted many a story and website to it, I belong to a weekly chat about it and a yahoo group.
Question is, how did I come to be so obsessed with the show when it aired when I was a mere infant? I have to catch myself nowawadays from making typos such as calling things “steele mills”.
Merla (whose alternate name and IM handle is MerlaSteele, for homage)
I don’t know if the OP is limiting to “police department detectives”, but I’d have to say…
Jack Bauer (“24”)
[list=1]
[li]Harry O David Jannson’s world weary detective was a classic[/li][li]Jim Rockford James Garner makes it look easy[/li][li]Banachek. Had you wondering the entire hour “How did they do that?”[/li][li]Joe Friday Just the fact please[/li][li]McGarrett Book-em Dan-o[/li][li]Honey West drove a Cobra, need I say more?[/li][/list=1]
Monk.
Emma Peel!!!
Frank Drebin.
Monk! with honorable mention to Lenny Briscoe of Law and Order and to Elliot Stabler of Law and Order: SVU.
Jeremy Brett as Sherlock Holmes.
Ironside. More moral authority than any other man on television. Plus the socially responsible plots, where he always saw past the superficial view. Definitely the 1970s anti-particle to Richard Nixon.
Columbo and Bulman as runners up.
Nick Yamana
Dietrich
Holmes (PBS version)
Most of my favorites have already been mentioned: Columbo, Jim Hutton’s Ellery Queen, Jeremy Brett’s Holmes, Inspector Morse (but it’s really Sgt. Lewis that I love).
What about Robbie Coltrane as the detective psychologist in Cracker?
David Jason as Inspector Frost. also i second Robbie Coltrane as Edward Fitzgerald (Fitz)
Thank you. It’s been awhile since I’ve seen them, and couldn’t recall what the character’s name was. I wish A&E or someone would rerun this series.
Columbo by a mile.