You can actually make a Pichu even learn Volt Tackle.
In Pokemon HeartGold and SoulSilver Versions, Pichu can hatch from an Egg already knowing the powerful Volt Tackle move. For this to happen, one of the Pokemon left at the Pokemon Day Care must hold the Light Ball. If you don't have one yet, the item is sometimes held by wild Pikachu.
An example of a pair that results in a Pichu with Volt Tackle.
Give Pikachu (Girl) the Light Ball and leave it at the Pokemon Day Care with a Cherrim (Boy), also from the Fairy Group.
After the Pokemon breed, then hatch the Egg that has Pichu in it. After Pichu hatches, level it up until it has a high friend ship. Once it evolves into Pikachu, then you have a Pikachu with Volt Tackle!
Source: Knowledge and the Pokemon HeartGold and SoulSilver handbook.
Hope this helps!