I have quite a few more than 10 here, but it was just so hard to narrow it down. I did, however, narrow characters down to book and/or series for 17 (30+ characters!). These aren't really in any specific order, but I do know one thing we would need a really big lunch table!
Most of the cast of Harry Potter - especially the Trio, Neville, and Luna
Katniss Everdeen, Peeta Mellark, and Finnick Odair from The Hunger Games
Celaena Sardothien from Throne of Glass
Blue, Gansey, and Ronan from The Raven Cycle
Cinder, Cress, and Carswell Thorne from The Lunar Chronicles
Cal and Niko from from the Cal Leandros series
Atticus O'Sullivan from The Iron Druid Chronicles
Sherlock Holmes and John Watson from The Adventures of Sherlock Holmes
Bilbo, Gimli, Legolas, Aragorn, and Eowyn from The Hobbit and The Lord of the Rings
Tessa Gray and Will Herondale from The Infernal Devices and Simon Lewis from The Mortal Instruments
Jon Snow, Arya Stark, and Tyrion Lannister from A Song of Ice and Fire
Levi from Fangirl
Harry Dresden from The Dresden Files
Isaac Vainio from The Magic Ex Libris series
The Doctor and his Companions from 2005-- Doctor Who (they have novels!)
Sam and Dean Winchester and Castiel from Supernatural - novels for them too!
Buffy and the Scoobies from Buffy the Vampire Slayer and the cast of Angel - novels too!