Over the years?
Hmm, number one would be Korbach Angist. That's his holy symbol that I use for my avatar that one of the very friendly artists on this site created for me many, many years ago. And the fantastic Hunter McFalls actually drew his portrait for me that's still floating around here too. Korbach began his existence as a 2e Priest of Kossuth from the Faiths and Avatars book. Loved the heck out of him and created a rather extensive religion for him. He then became (many years later in another group) a 3e Half Fire Elemental cleric (using a template from Dragon Magazine) that I just adored playing. Later, he came back again as a Forge Priest of Kossuth in a Storm King's Thunder campaign.
I am recently toying with bringing him back once again in a one shot game as a Circle of Wildfire Druid, still worshipping Kossuth - which would probably be the closest I could come back to his original 2e incarnation.
Believed that fire would purify the world and that water was the physical embodiment of evil. So much fun to play.
Number 2 would probably be a 3e gnomish binder that I got to play in an Eberron campaign. LOVED playing him. Being able to play a, more or less, completely new character every session was just so much fun.
Number 3 would definitely be a warlord I played in 4e. Playing a warlord just hits all the right buttons for me. An eladrin warlord was just a total blast to play but, unfortunately, that campaign got cut rather short and I never got to explore him too much.
Coming in at number 4 would be Sethalarmis. A human rogue who believed that, after eating a stew made from some questionable mushrooms, he was visited by Kord who commanded that he wander the world, seeking to create a tabernacle to straighten crooked men and tighten loose women. He truly believed that the spoon he carried was a holy relic. Based strongly on Lucifer Jones of the fantastic Michael Resnic books. He was SOOOO much fun to play.
I really do wish I got to play more. Four characters spread over nearly thirty years.

When I do get to play, I just pour my heart into it.
Those of you out there who always play and never DM? I am so jealous of you.