A hobby can really ad some extra characterization to your character in my opinion, and if you think hobbies are for middle aged moms in their mid life crisis then think if it as "Things your character likes to do when their not in the middle of saving the world." or something like that.

Some of the best characters have hobbies, for example:

Harry Potter: Hermione loves to read and study, it would be really weird of Hermione didn't have that hobby, and if she didn't have it the plot for Harry Potter would be a lot  different.

The Hunger Games: Peeta is good at making bread because of helping his parents in the bakery, and I wouldn't call it his hobby, but definitely a talent. Also it leads to his hobby: Painting

The Mortal Instruments: Clary loves to draw, and it provides a important part to the book/books later on.

So hobbies can be pretty cool for you characters to have, I make sure ever one of my characters has a hobby or two, sadly I'm horrible at finding the right hobby fore them, so hopefully this list of hobbies will help me and you.

HOBBIES:

Archery

Bagpipe playing

Baking

Ballet

Baseball

Basketball

Biking

Bird watching

Blogger

Boxing

Card playing

Cello player

Chess playing

Collecting things

Composing music

Concerting

Cooking

Cosmetology  

Cosplaying

Crocheting

Dancing

Drawing

Eating

Exploring

Falconry

Fencing

Figure skating

Fishing

Flute player

Football

Gamer

Gardner

Golf

Harpist

Hiking

Hockey

Horse rider

Hunting

Irish step dancer

Karate

Knife throwing

Knitting

Kung Fu

Lacrosse

Magic tricks

Meditating

Music lover

Palm reading

Painting

Painting nails

Photographer

Pianist

Playing guitar

Playing ukulele

Pottery  

Reading

Rock climbing

Scuba diving

Sculpting

Scrap booking

Sewing

Singing

Skateboarding

Skiing

Snowboarding 

Stargazing

Surfing

Swimming

Tap dancing

Tarot reading

Tennis player

Theater kid

Violinist

Whittling

Writing

Yoga