This is a hard one. I love mysteries and most of the ones I read are in a series with its own detective. Probably my favorite historical detective is good old Sherlock. I've read all the short stories and novels (or novella's really) but for a modern detective I can't decide. I will limit my list to characters who are actual detectives, not friends and neighbors who get caught up in events, so...
1. Robert Colbeck, Scotland Yard detective in 1850's era England by Edward Marston
2. Lena Jones, private detective in Arizona by Betty Webb
3. Kinsey Millhone, private detective in California by Sue Grafton
4. Maisie Dobbs, private detective in 1930's era London by Jacqueline Winspear
5. Phryne Fisher, private detective in 1920's era Melbourne by Kerry Greenwood
6. Stanley Hastings, private detective in New York by Parnell Hall
7. Chet and Bernie, private detective, Chet thinks they live in Arizona by Spencer Quinn
8. Molly Murphy, private detective in 1900's New York by Rhys Bowen
9. Harvey Marmion, Scotland Yard detective in WWI London by Edward Marston
On top of all these are all the amateur detectives who solve crimes before the professionals can and sometimes before they even know there's been a crime. I love mysteries!!!
One day I was sitting around feeling sorry for myself because I was getting older and knew one day my brain would turn to mush. Then I had a bright idea! I would read every mystery book in the library. It would keep my mind busy figuring out all the puzzles and I'd be entertained too. It's a great way to stave off brain mush!!! Sadly, for all my reading I don't think I'm going to be able to finish all of them--but I'm still trying...