Say I'm a Fighter with the Double Slice feat, wielding a sword and a shield with a shield boss or spikes. Does the shield qualify as a 'weapon' for the purposes of attacking with Double Slice?
Would it qualify without the boss/spikes?
Shield does count as a weapon (1d4 in the weapon table) even without boss/spikes. Though at higher levels you can't get potency runes or special abilities on a bare shield but by that time you should be able to get a boss/spikes no problem.