When you know that your probably not going to finish your Y solo run with a noibat.

well Mr grant I see your a rock type gymleader with only 2 pokemon a tyrunt and a amaura. Oh your gonna send out amaura 1st ok let me use my sp.atk battle item and then it will be easy
Amaura used take down
oh a normal type move cool this gyms going to be easy
IT WAS SUPER EFFECTIVE!
wait what....

Gamer's mathematic mode activates
Noibat = Arcamedes = dragon/flying = 4x weakness to ice 2x weakness to electric and 2x weakness rock
Amaura = ice/rock type 
takedown = normal type move
normal type move + dragon/flying type move = apparently super effective

and now its time to google on serebii amaura

(gamer realises that amaura gets refrigerate)
well my noibat is level 30 and apparently cannot take a hit form a lv 25 refrigerate amaura
its either more grinding or I bring froakie out of the pc.

*claps* Good job Gamer. That proves that you always need to prepare first before you go into battle. Amaura was even shown with it's ability refrigirate. Just like Tyrunt was shown with his ability, strong jaw. It's almost their signature ability.

Also, Noibat isn't weak to electric. Dragon resists electric. Noibat is weak to 4x ice, 2x rock, 2x dragon and 2x fairy.