must I even explain myself! xD

nearly all the others he would probably fight, this idiot ~.~

Erza is strong, but she's not compatible to fight together with Natsu. From your list, I think the most compatible one to fight with Natsu is Gajeel. They already beat Laxus and fight Sting+Rogue.

gray :3 if they put their mind to it, they can do anything xDD heck since fire and ice are compatible with eachother in fighting~

I personally think Sting

i think rogue will make a best powerful team with natsu.......natsu eating the shadow.............and a fire shadow dragon is born.................no one can touch the shadow,.................he he he he

Laxus, Because Natsu can eat Laxus's thunder 8D
Erza is strong, but I don't think they can be together in a team, "Just sometimes they can be :V"
Gray is making problems always with Natsu, so NO lol
Gajeel is as Gray ... NO :D
Sting isn't bad, but he hates Fairy tail ._. So NOOO
Rogue.... NO I hate him D:
Mirajane is great, she can be with him, but still I prefer Laxus :D

Kind of complex to choose. XD They all are great in their power, defense, and strength but I think Erza is the best candidate for Natsu. Besides, their friendship is extra powerful and nothing can beat the power of friendship.