OP skills you can think of

Boots' movespeed now STACK

Changed my Crystal Maiden item build to 6 boots.

On the topic of OP changes:

Laguna Blade now bounces between enemies like Chain Frost.

Freezing Field stuns all enemies hit by an explosion for 1.5 seconds.

Sacred Arrow heat seeks target hero and cannot hit any other unit in it's way, infinite range until it hits target.

Boots' movespeed now STACK

You can now put all your skillpoints into one skill, and it will scale according to how it scaled pre-level 4

Black Hole Now creates a real black hole... DESTROY THE EARTH.

Actually...this genuinely happened to me once.
So I was playing Legends of Dota and I had Black Hole, Divided We Stand and Rearm (yes you can have multiple ults in the mode, yes this is broken ^^)
So I ran around the map blackholing everything that moves, and after a while, THE BLACK HOLES ACTUALLY REMAINED AFTER THEIR DURATION. Just like real black holes, actually. They just stayed there and continued to suck in creeps and heroes indefinitely. It's more realistic this way...once you're past the hole radius it's done for you.
And then after a while the game crashed. The gravitational instabilities actually destroyed the DotA universe.