I liked how they balanced comedy and shounen moments, although there are mentions of being in war, death, and fights, it still keeps it's gag moments. It was a great anime to watch over the summer.
I was a bit depressed when I found out that the mangaka for Gintama originally planned Hijikata to be the main character, I think that he was one of the most interesting characters.
My favourite episodes all have to do with side characters, it's strange how most of my favourite characters are usually the secondary character. Episode 31-32, when Gintoki lost his memories; 86-87, when Okita Mitsuba visited Edo; 101-105, when Hijikata almost lost his position in the Shinsengumi; 114, when Hijikata had to keep boys away from the daughter of the head of the police department (first met in episode 35, 2nd half); 39, when Katsura hid from the Shinsengumi in the ramen shop; 187, when Sougo revealed the truth in a past case.
My favourite character has to be Hijikata Toushirou, I like how he has a complicated past, yet try and make a simple future. His "code" is also worth complementing, which is the way he carries other's burdens on his shoulders. Although it is often told in mangas that their friends would not allow that, I still find it cool.