You receive some pretty awesome presents. You are in awe of them; you had not imagined that mere humans could produce something in such atrocious taste, let alone several things that bad.
Alternate wish: I wish to be able to transform into any pokemon I want to, and to be able to transform back into human form.
You gain the power, but you're always level 1.
That's not much of a corruption. Level one Ho-Oh can produce Sacred Ash, which is a panacea. Turning into the legendary birds and dogs, the Hoenn weather trio and the Unova djinni allows weather control, so no more natural disasters, ever. Throw in a large number of telepaths and telekinetics and optimising human civilisation is going to be a lot easier (no more lying on matters of public interest ever again, for example, and no chance whatsoeever of an ICBM hitting its target). The Sinnoh dragons allow complete manipulation of spacetime and access to arbitrarily large amounts of antimatter, so we have effectively infinite energy and can colonise the universe. Arceus is is the creator god of the entire Pokemon universe. Yeah, sure, I'll take those powers at level 1!
Alternative corruption: you can turn into any Pokemon, but you're unable to use any of their abilities that can't be naturally used by another Earth lifeform. (You can still fly, burrow, breathe underwater, run really fast, lift elephants and survive extreme temperatures and pressures - wishing to turn into a Pokemon is too good for me to really cripple you.)
You have one; the first time you use it you accidentally cross paths with yourself, creating a paradox in which you and yourself are sucked through a tear in the fabric of reality and crushed into a singularity. The tear you made in the universe remains a source of strange events, so the military build a base over it, spawning an outbreak of area-51-esque conspiracy theories.
Also, I have no idea what MoR stands for; the Time Turner appears in the Prisoner of Azkaban.
Ask Google; it's by far the best HPverse fan work and almost certainly the most famous. I specified a non-canon version because they don't work the same way (because the derivative work has characters who act realistically and intelligently, rather than to further the plot, and the canon version is horrendously abusable). That corruption completely violates the way that both versions work; the only problem with meeting yourself is that you are obliged to do anything you observe your future self doing.