Abstraction of a proton in cycloheptatriene
The pKa for a vinylic proton is ~ 43, the pKa for propene is ~ 40, and the pKa for 1,4-pentadiene is ~ 35.  Consequently it's not the vinylic protons that are the most acidic, it's the allylic ones.  Now the question whether tropylium anion is aromatic/antiaromatic is complicated.