Good list Cormac!
1. 65,000,000 years ago: to see the Chicxulub impact occur and the aftereffects.
I might add that one to my list - although I tend to concentrate on human history
2. 6,000,000 years ago: to see Argentavis Magnificens in flight.
Got me on this one - I'll have to go look it up as I have no idea what it is! I presume a large bird?
Went and looked that up
Yep one big chicken I'd say
2000 BC: To see the people and setup of the Shofukuji Site, Kurume City, Fukuoka Prefecture, Japan
This is an interesting one too as I know little about it...dang more research. Must learn to do without sleep