Kingo works for MK2. I can confirm it worked with no added instability or apparent issues on the 2 I337 devices I've messed with. But is it reliable? Well, it does send your IMEI to a Chinese server for some unknown reason. You can try Vroot if you want but it's definitely not as 'user friendly' if you catch my drift.
Samsung SPH-N200 (1999ish-2001)
Samsung T100 (2001-2003)
Moto RAZR V3i (2003-2005)
Nokia 6620 (2005-2007)
iPhone 3G (2009-2012)
Samsung GS2 Skyrocket (2012-2013)
Samsung GS4 (2013-Present)
Hit THANKS if I was helpful, and you shall be blessed greatly.