Vampire - All biting moves restore the user's health by 50% of damage dealt.
I'm not doing Sand Claws because I think Tough Claws is the ideal ability for Mega Sandslash.
As for Raichu, I've chosen for the physical Mega Evolution, and to give Raichu Fire Punch, Ice Punch, Aqua Tail, Play Rough, DynamicPunch, Dazzling Gleam, Energy Ball, and Signal Beam.