I would like to mention Iron Fist as a good secondary ability choice. It's an ability that is clearly made for certain builds which is why it would be a good second ability. I support the more physical side of this poke personally and as such it shows great potential for sub-punching as well as weighing thunderpunch against thunderbolt, which seems to be a big reason why people are trying to make to make this poke more special sided, which personally I think is a little misguided. For example most of the special sided wants are to use Draco Meteor and Thunderbolt. Draco Meteor can be strong but it halves our Sp. Att and we've already decided to make a slightly defensive poke so it won't be very high to begin with, which then leaves us to switching out more. Which with this poke who faces many common SE moves, is not such a great idea to have to switch out a lot. Thunderbolt over Thunder Punch is easy to see why people are choosing it (because of the 95 to 75 power comparison) but lets remember that dragon is our more reliable STAB attack as it is only resisted by Steel and SE against other dragons who may want to switch in on an expected electric attack. Electric is resisted by three types (one being dragon who may try to switch in on these and outspeed for STAB+SE) and utterly nullified by ground which is going to be a commonly seen counter for this poke. Also, if power is so important why not go for iron fist then and throw some STAB+20% increased Thunder Punches around?
We could choose any other ability, the good ones that have been mentioned so far in my opinion are Rough Skin, Static, and Shield Dust. Then we could choose iron fist as a valuable secondary ability for people who want to use this slightly defensive poke to attack. Switching in on something that can't damage us and throwing up a healthy sub while they switch to a counter just to get hit with a massive Focus Punch (boosted 20% by iron fist). Then to be either outspeeded (depending on chosen stats) by a 20% thunderpunch/other move of choice or a priority move is a nice build option IMO.
Edit: Also, just in case anyone was wondering here are all the moves boosted by Iron Fist:
Bullet Punch, Comet Punch, Dizzy Punch, Drain Punch, Dynamic Punch, Fire Punch, Mach Punch, Mega Punch, Meteor Mash, Sky Uppercut, Ice Punch, Focus Punch, Hammer Arm, and Thunder Punch.
We could choose any other ability, the good ones that have been mentioned so far in my opinion are Rough Skin, Static, and Shield Dust. Then we could choose iron fist as a valuable secondary ability for people who want to use this slightly defensive poke to attack. Switching in on something that can't damage us and throwing up a healthy sub while they switch to a counter just to get hit with a massive Focus Punch (boosted 20% by iron fist). Then to be either outspeeded (depending on chosen stats) by a 20% thunderpunch/other move of choice or a priority move is a nice build option IMO.
Edit: Also, just in case anyone was wondering here are all the moves boosted by Iron Fist:
Bullet Punch, Comet Punch, Dizzy Punch, Drain Punch, Dynamic Punch, Fire Punch, Mach Punch, Mega Punch, Meteor Mash, Sky Uppercut, Ice Punch, Focus Punch, Hammer Arm, and Thunder Punch.