I vote for the Body Leech PrC. It's a Psionic character which traps creatures in Ectoplasmic Cocoons and can inflict Ability Burn to them to recharge their own PP, but at 5th level it gets the ability to, when it dies, swap minds with a previously determined cocoon captive, going into their body like True Mind Switch without the XP cost.

Though honestly the Ghost suggestion above is the easiest method.