I know they’re not the most popular, but a Nexus original character inspired by the random character selection avatar.
He would start the game as a random hero, so the enemy team won’t know who he really is, and have access to all that hero’s abilities. He would also be able to morph into all enemy heroes, but would not have access to any of their abilities (plus, doing so would reveal him). Random would assimilate hero abilities after enemies used abilities on him. For instance, if Varian charged him, Random would be able to morph into Varian and use his charge ability and so on. Every time an enemy used the same ability on him, Random’s version of that ability would be strengthened. So, he would have a sort-of Zul’jin like playstyle.
His talent choices for his original form would be the player’s choice. The talents used on his other forms would remain untalented, however, the damage/heal output of each ability would increase without limit
His trait would be morphing, and would be able to use keys 1 thru 5 to morph into a different hero, incurring a 10 second or so CD.
At level ten he would choice between two passive heroics; the first of which would be Flux. This heroic would attempt to perfect enemy abilities, but will result in a flux which would take the form of flipping increases and decreases to CD and damage/heal based on the number of time Random had been attacked using those abilities. For instance, after taking this heroic Random uses an ability whose damage output and CD have be doubled. The next time Random uses that same ability its damage output and CD would be (respectively) half the pre-heroic damage output and CD.
His second heroic would allow him access to untalented enemy heroics. The heroic ability for each enemy hero would increase in strength each time it was used on him (and he was able to gather data regarding that heroic).