Charging shoulder slam?
Jumping wicked intentioned "what's up bro" chest bump?
Sidestepping a thrust attack by an enemy and pivoting your spiky armor towards his face?
Yeah, i usually picture the shoulder slam or forearm smash. Look at some of the pictures of spiked armor, their wicked design can be pretty inspiring.
Also a nod to Thimbledorf Pwent for Rocking Out in spiked armor. Who needs to "attack" when you can just treat the battle field like the pit at a Slayer concert.
If you have a KEWL #1 Ace DM, get masterwork armor with masterwork spikes. Then enchant spikes with the Dancing enchantment: uppon command, they'll magically detach from the armor and fight for you...kind of like the spheres from the Phantasm movies.
underlooked....it can be used as a off hand attack but it does not give you two wep style as a feat...its also considered a light weapon and you cant be disarmed.