Thanks to XDA Developer, Chainfire (Donate him) for his CF-Root for Samsung Galaxy S II. Basically, CF-Root is a modified kernel based original firmware kernel by adding root to it. Besides, it also adds BusyBox, Superuser, ClockworkMod recovery and CWM Manager. It is one of the ways to root Samsung Galaxy S2.
Yes, I learned something new today. All the while, most of the Android builds that I tested came along with Superuser application by xda-developer, ChainsDD. And I did not bother what are its functions. I tried Moto-Mytouch 4G V0.4 alpha Android build. It was rooted but I cannot take screenshot with Screenshot application due to no root access permission. Huh? That build is rooted but I failed to access root. So I installed Superuser application from Android Market. Granted Screenshot application access to root. And it is working like a charm now.
Superuser for Android