Um, well what about drawing, watching tv, sleeping, reading, creating things on power point, write, paint, sketch dresses, build something, help people on here (lol), design t-shirts, color, watch movies, write a script for a movie, write songs, sing, depends what you're interested in.
What is cool is subjective. Here are, in my opinion, cool things: Knitting, crochet, chainmaille, baking, video games (check out mine craft! lol Also Steam has a sale right now steampowered.com), scrapbooking, sewing, writing a book (check out nanowrimo!), reddit.com (you'll never emerge!), watch Doctor Who because bow ties are cool, try learning programming.instructables.com
The best but not too cool hobby is try writing and publishing stories.You can even earn money and develop it in to a hobby.You can learn to play musical instruments.But never make internet as your hobby because it is very addictive and stressful.Not only that you will develop carpel tunnel syndrome.You can also learn new languages.Try to build a tree house if you have space for it.Buy a pet a play with it,understand it and interact with it.Explore haunted places in your area and go take videos.pics etc.Don't go alone.Go with a friend.It will rise your adrenaline.Choose something interactive,interesting and healthy. Have fun.
I think war-gaming miniatures is a fun hobby. The great thing about it is that its a multifaceted sort of thing; there's a sense of creative accomplishment in building and painting the miniatures, and apart from having cool little figures that you can display, you can also use them to play and fight against other people in the community (which by the way is really really collaborative and friendly). And aside from that you can also really get lost on the lore. So its pretty much a combination of model-making, board gaming, and reading all within a network of really helpful and passionate individuals.
I think programming is a good hobby, as it has wide applications, looks impressive and I find that making games can be funner than playing games, as you create what you want, and release your imagination. There are a variety of free (and paid) programming systems, but which one you choose is dependant on your skill set. Beginners could use Scratch then advance to Game Maker (which has multi-platform outputs, including phones) and if you have a good understanding, you could try Unity and Python (which there is countless tutorials about). Scratch, game maker and unity all have free versions and python has a free compiler. I prefer Unity as it is a good balance between speed of creating the game and the amount you can do with it. All of the previously mentioned game engines also have a popular community, where you can find tutorials, examples, game materials and forums full of discussions, which all enhance the experience. So that is my recommendation (Game Maker, if you are new to programming) as it can be fun and interesting. Good luck deciding your hobby :)
We cannot tell you what you think is "cool". The things we like may not necessarily interest you.
Take all the recommendations on this comment section under advisement and just try a bit of everything. For that matter, do not take activities demanding physical effort off of the table unless your health disallows it.
Open yourself to new hobbies and you will eventually find something that interests you.
Board games is something I always found is a great way to spend time (and if you want to buy a good intro game, get either "Settlers of Catan" or "Avalon"), or pick up a instrument! As someone who has been playing a bevy of instruments for more than 10 years, I cannot even effectively communicate the ways music has improved my life