The magus class allows them to do two very special things, add weapon damage to spells that normally would not benefit, and have higher crit ranges.
However it occurs to me that it might also allow something else, something possibly quite powerful, and that is the inclusion of vital strike on spell damage.
When you use the attack action, you can make one attack at your highest base attack bonus that deals additional damage. Roll the weapon’s damage dice for the attack twice and add the results together before adding bonuses from Strength, weapon abilities (such as flaming), precision-based damage, and other damage bonuses. These extra weapon damage dice are not multiplied on a critical hit, but are added to the total.
Now when it talks about the effect, it always mentions the weapons damage dice.
At 2nd level, whenever a magus casts a spell with a range of “touch” from the magus spell list, he can deliver the spell through any weapon he is wielding as part of a melee attack. Instead of the free melee touch attack normally allowed to deliver the spell, a magus can make one free melee attack with his weapon (at his highest base attack bonus) as part of casting this spell. If successful, this melee attack deals its normal damage as well as the effects of the spell. If the magus makes this attack in concert with spell combat, this melee attack takes all the penalties accrued by spell combat melee attacks. This attack uses the weapon’s critical range (20, 19–20, or 18–20 and modified by the keen weapon property or similar effects), but the spell effect only deals ×2 damage on a successful critical hit, while the weapon damage uses its own critical modifier.
So lets take the common build of a magus with a rapier and shocking grasp. The caster level will be higher than 5 so the spell damage will be 5d6 due to the BAB requirements of vital strike being 6+. So lets assume that the spell was cast on the last round so we can ignore spell combat and action economy and focus solely on vital strike and spellstrike. So assuming the attack is successful (and not a critical hit, since that critical damage does not actually matter in this case), the rapier damage is 2d6, but what about the extra spell damage? Does the spell damage get considered as part of the base weapon damage and becomes 10d6, or is it considered extra damage like the flaming weapon property and strength and not increased remaining at 5d6?