Time Travel!

[blackmage_nuke]

If I go back in time with the clear intention of changing something, then I'll have lost the need to change something once I change it, so we'll have a nice little paradox there.

Not quite, it just means you create an alternate timeline but if you've altered it enough so your future self never goes back in time when you get back to the future there'll be two of you there. So if you invest stock into something make sure you do it under a false identity, otherwise your alternate self will be rich, and if you were a rich bastard would you spare a penny for anyone? Even yourself from an alternate universe?