Dota 2 has a lot of funny game quotes. Best thing is that you can use your characters quotes in game, which can be pretty fun after for example you score a kill.
Some funny ones:
Enchantress:
"I'm a predetor" (While being a "Bambi-like" character)
Omniknight:
"Beutiful" (Pretty fun to use after you won a team fight xD)
Teachies:
"Fun" (teachies used to be (and still kind of is) a kind of trolly hero that placed mines, so saying this after you got a kill by people walking on your mines is kind of funny)
"Planted, like a tree" (When planting mines)