I’d open a restaurant that serves dinosaur egg omelets. I’d make it clear that the eggs could be incubated and hatched, but I’d just make omelets. I’d give zookeepers and so forth the impression that I could be persuaded to provide eggs for hatching, but with no intention of actually doing so.
Create thousands of inscribed small plaques made of some very durable material then cause them to end up deeply embedded in coal seems.
Half of them will be inscribed with “Jesus is Lord”. The other half will be inscribed “There is no God but Allah and Mohammed is his prophet.”
I’d position a director’s chair and a little end table with various mundane items that look as if they’ve been carelessly left in the shot – maybe a can of Coca-Cola, probably some cigarettes in a cut-glass ashtray, almost certainly that morning’s newspaper – right as Neil Armstrong starts in about how “That’s One Small Step…”
I’d release a bunch of wolves to eat your rabbits. 
I knew that.
I’d reverse engineer the time machine, then build thousands of them (using my lottery winnings and market profits). Then I’d sell them for the cost of postage in the first Sears catalog in 1888.
I’d travel back to 1964 and introduce Strom Thurmond’s black love child to the voters of South Carolina.
I’d introduce the word “assclown” to the English language during the Nixon administration.
Go back to late November 1941 and convince the USN that their aircraft carriers would be much safer anchored at Pearl Harbor.
I’d fool around with the 2008 elections so that John McCain ends up choosing a ditsy former beauty queen as his running mate.
I’d send a memo to the Apollo 13 mission planners: “Duct tape? What the hell are they going to need duct tape for?”
I’d kidnap major Christian leaders and let them watch the crucifixion. And then fast forward the machine a bit so they can watch His corpse rot on the cross, in clear contradiction to the gospels.
Then I’d return them to their homes and keep track of which of them holds on to their faiths and how long.
some sample downfall videos when I searched youtube
[ul]
[li]Hitler reviews Transformers[/li][li]Hitler Reacts to new Morbid Angel Album[/li][li]Hitler reacts to the news that Osama bin Laden was killed[/li][li]Hitler rants about C&C Red Alert 3 DRM Install Limit[/li][li]Hitler rants about his website being hacked[/li][/ul]
The problem here would be trying to explain the 21st century terms to him. But hey go for it.
It might be amusing to pop into Hitler’s office and leave a modern map of the Middle East - dated, of course - complete with Israel and a little Israeli flag pin stuck in to it to make sure he notices. And a roll of swastika toilet paper as a paperweight.
Nah, that wouldn’t change too much since people already follow those religions and already fight over it. I’d inscribe them with something like “Anu is the one true King of the Gods, and if his worship ever ceases he shall destroy the afterlife and the souls of any who thereafter die until the end of time”. Or “Fear the wrath of Lucifer, who has pulled down Jehovah from his throne and made himself Lord of All.”
I’d go visit Isaac Newton and get him laid with some high class whores and/or hookerbots.
Visit the Pacific Northwest a million years ago and get some pretty sweet lookin’ Bigfoot tracks fossilized.
Go to ancient Egypt, steal some porn tablets advertizing for the next orgy, then bury them on some random hill in New England.
Leave a large, laser engraved slab of stone that says FIRST!!!1!1 on the far side of the moon. In Russian.
Have custom made “alien rifles” built; guns obviously not designed for a human user, with what looks like nonhuman writing engraved on them. Then have thousands of them buried just before the extinction of the dinosaurs where some are sure to get fossilized.
It all depends… can I fit a T-rex in my time machine?
If I can fit a Tyrannosaur in the machine, sometime in the late 200s I’ll drop off a dead Tyrannosaur with a lance through its chest, somewhere where the remains won’t be found until modern times.
Me I would go back and get the USA to elect a complete dimwit to the Oval office - someone like George W Bush… Ooooops - Me - no I dont own a Time machine - Honest.
Go back in time and steal all the prop weapons from District 9. The command module while you’re at it.
I’ll also make 50,000 copies of Gray’s Sports Almanac and sell them in 1985. Only the scores will be randomized in each one.