Gin-chan is my number one, it reminds me of the ranking episodes that were so funny especially because they were true. After that comes Kamui, Hijikata, Okita and Tsukuyo, but I love all Gintama characters, I can't hate either one of them (I think this is the only shounen where I don't dislike any character).
My favourite from episode 1 has been Okita, and I guess it hasn't changed. I thought it was funny that he was introduced as the strongest swordsman in the Shinsengumi but it took awhile for him to take out his sword since he was always using the bazooka lol. Well that's changed in recent episodes, but he's been my favourite for so long lol. He's still funny for different reasons though lol.
If it wasn't for bazooka reason, Gintoki would've been #1 for sure lol. He's super cool \(^0^\ )