First, a cool little different-mood acoustic take by Noella Choi:
Nice, eh? Whole different feel.
In a similar mood — not great video, but a sweet acoustic version:
Now a funny one. Not great sound, kind of bizarre performance — but dude, check the guitarist. For a high school level performance? Surprisingly good!
Then, at no extra charge: did you know that Chicago itself did a re-take on the song?
Finally, to wake you back up and send you on your way, a surprise to me. No idea Vince Neal of Motley Crue did a metal-style cover. And not half-bad!