I would like to use a Pikachu on my team, but without a light ball it doesn't compare very well to a Raichu. Is there anyway to get one in Pokemon X and Y?
According to Serebii.net Pikachu has a 5% chance to hold a light ball (the same as Black 2/White 2).
I decided to do some testing out in the field with a Vivillion (Compound Eyes) and Shuppet (Frisk, Thief):
Route 3: Encounter rate too low for workable results
Santalune Forest: 1 Light Ball / 10 Pikachu
Friend Safari: 3 Light Balls / 20 Pikachu
Accounting for slight variations, we can assume a 10% chance that a Pikachu holds a Light Ball, although this is accounting for Compound Eyes.