Im talking about having the ability to take the role of 2-3 enemy champions with maybe 3 kills no deaths.

Ones i know: Udyr, Shyvanna, Tryndamere, Kassadin. Any others?

Teemo.

I hate when Teemos get fed. They come out of no where and spit darts like no ones business.

Fiddlesticks can solo 3+ people if he gets fed. With a crowstorm gank into fear and drain, he will definitely kill at least two if not more.

Pretty much any champion that is fed can do this it also depends on the team your going up against. One of my favorites is a fed mord though 1v5 turns into a 2v4 using there carry to kill them 4 pentas from that :)

Morde, i have killed four on my own lol

trynd or nasus

If Vayne gets fed she is going to shoot my face off.

Twitch, Vayne.

Nasus
Tryndamere
AD Sion

In crazy situations Veigar--I've seen his calldown oneshot three champs at the same time

OP stated Shyvana, which I can actually agree with. I used Shyvana quite extensively on TT for a while, and many times I dropped down to bottom lane to hit the enemies as they retreated and got a triple kill, 3v1. She can be pretty OP if geared to the teeth.

Another person I've decked out and gotten several kills solo: Shen.