Whimsyshire Exploit (All Difficulties) - Range trick : Diablo 3 Nerfed Info

This tip will work better for ranged classes, but if you're a melee character I'd recommend using at least 1 ranged attack like "throw weapon" to take advantage of it.
Basically, if you've done an Inferno Whimsyshire run, you're aware of how tough the Unicorns are. I'm a Wizard with somewhat high def, resists, and average vitality, but even with a hit or two from the unicorns and I'm out cold. What's worse is that you can't out run them (at least with 12% movement). It's even worse for the Elites and Champion Unicorns, since they're typically 1 shotters.
So, what I recommend you do when encountering any type of Unicorn (excluding teleporting) that you know you can't easily take down (typically the Elites and Champions) is that you get them pinned. There is one spot in particular that always spawns on every map and that you need to look for. I'm including a screenshot so you can see what I'm talking about, but it's just a tree that is ever so close to the edge which allows you to pass through it, but stops Unicorns from doing so.
Once in position, the Unicorns will be locked in place and you can simply spam ranged attacks easily killing them. Generally most of the Elites and Champion packs ARE unicorns which makes this method extremely helpful. So, while it does NOT work for the Cuddle Bears and Flowers, it will work for the more common Elite/Champion unicorns.
Well, hope this helps someone!

Nerfed