ehhh....pikachu isn't really that bulky....
horrible defense, and the highest base stat it has is speed, being at 90.
90 is decent speed for any Pokemon but pikachu deserved a little better :P
Evs: 252 attack 252 speed ._.
Item: Light ball (of course)
Fake out (it has priority and makes the opponent flinch b0i)
Quick attack. (if they are about to kill you, might as well get a little more damage up in there.)
Volt tackle (if they are just trying to set up, or you just happen to survive, i'd go to volt tackle :3)
I was going to put roar here, but pikachu cant learn it. fluff sake. DAMMIT roar wouldve helped ;-; I guess put protect here or whatever else you want. suppose its up to you from here :P