Jailbreak iOS 6 without cydia
If you have a device that supports iOS 6 and is vulnerable to limera1n (iPhone 4, iPhone 3GS, or iPod touch 4th generation), you can use redsn0w to jailbreak 6.1.2 tethered without installing Cydia (just uncheck the "install Cydia" box during the jailbreaking process).

redsn0w hasn't been updated to automatically support 6.1.2 though, so before clicking the "Jailbreak" button, you'll need to click "Extras", click "Select IPSW", and select a copy of the 6.0 IPSW for your device. You'll also have to do the "Select IPSW" process before booting tethered (in other words, when you want to boot your device, you'll have to click "Extras", "Select IPSW", select the 6.0 IPSW, and then go back and click "Just Boot").

It's probably less fuss to just jailbreak with evasi0n, open up Cydia, let it prepare the filesystem, install OpenSSH, and then look for the "Cydia Installer" package and uninstall it.