Because you like Anya Jenkins in Buffy the Vampire Slayer
Rukia Kuchiki is a cool and collected warrior who has trouble opening up to anyone. See them in Bleach.
Konata Izumi has a live-now, worry-later view of the world. See them in Lucky Star.
Wei Shen is an undercover cop on a mission for justice (or at least vengeance). See them in Sleeping Dogs.
Sheldon Cooper is brilliant in every way except, well, interacting with any human being. See them in The Big Bang Theory.
Misato Katsuragi is never without a beer in her hand or her pet penguin by her side. See them in Neon Genesis Evangelion.
Ellie is more world-weary than most 14-year-olds. You would be too if your world was infested with zombies. See them in The Last of Us.
Whether he's fighting or flirting, Jace Wayland is all swagger. See them in City of Bones.
Don't worry about this forensic scientist offing you unless you're a serial killer yourself. (You're not, right? Just checking.) See them in Dexter.
Stranded on Mars, Mark Watney is armed with quick wits, an electronic diary, disco music, and an undying resolve to make it back. See them in The Martian.
Whether it's punching a meteor or saving a teen from jumping, Superman tries to be in as many places as Kryptonianly possible. See them in DC Extended Universe.
Handsome Jack is wearing a mask of his own face to hide his scarred real one. See them in Borderlands Series.