So here we go in no particular order.
The heart and soul of True Blood season 1. His role diminished in season 2 and sort of ruined the character, but his season 1 character was great though. Comedic, soulful, and edgy. He played a straight gay character, somewhat similar to Dafoe in Boondock Saints.
I can't pinpoint it exactly, but sometime after the show came back from the grave the writers thought it'd be good to turn him gay. So every episode, instead of trying to rule the world, he's just make funny quips about whatever and spout off some gay innuendos. Personally I thought it was for the better. Trying to rule the world got boring and really, giving him a personality was a great idea.
Now, he never actually came out in the show, but it's pretty obvious that he's gay. From the road map with all the rest stops rated, to his crazy and outlandish costumes or even his unabashed love for series lead, Jeff Winger. He brings hilarious gags to an otherwise humorous but not laugh out loud funny show.
There you go, my personal top 5 list of gay characters on TV. You may notice a lack of a lesbian characters, but I honestly can't think of many shows I watch with lesbian role.
--Edit-- Seems I didn't clarify what the list was, it's gay characters currently on TV. And yes, Omar Little would definitely be number 1.