Sideswiper key? I'm not certain I know what that is but ...

[KA0HVE]

I don't believe the Cootie is fast than a straight key. The Cootie key was invented as an alternative to the straight key and to give some relief from "glass arm" or carpal tunnel syndrome. It became obsolete when the "bug" was invented.

The Cootie key is keyed back and forth; right, left, right, left, with whatever element is next being sent on the next left or right alternation. For example CQ is sent right (dah), left (dit), right (dah), left (dit),...right (dah), left (dah), right (dit), left (dah). 

The original was the Bunnell Double Speed Key.  You can send a dit or dah with each movement in either direction.  Some operators go to it because they can key faster than with the traditional up-and-down telegraph key and it's considered a straight key.  The next faster straight key is a bug.

Yeah, it was considered obsolete but:  http://www.sideswipernet.org/  as DJ1YFK  listed above.  There is quite a following.

[K7MH]

I prefer the term "double speed key" which is also a common name, to sideswiper.
The Bunnell is a beautiful key and very expensive when they show up for sale. I'd love to have one but they are too pricy.
There are those who can really scream along with one but it takes a lot of practice. You'll find some videos on YouTube of guys that really have got it down.
I made my own with a hacksaw blade and some coffin key parts I came across.

[N0JL]

Daniel, a sideswiper CAN be faster than a straight key, but the main thing is it is significantly easier on the wrist.  A sideswiper is equivalent to two straight keys, on edge and back to back.  You can make a dit or dah on either side and alternate elements in a left-right-left motion.  I enjoy one a lot, although I also use SK, bug, and an iambic paddle for CW traffic. (no snide comments needed.)  Find my phone number in an old QST and give me a call.

Jim, N0JL
SKCC 2079T
Manager, CAN Cy4