J.
Hi - I too have a 2 (almost 3) year old that can be so wonderful, and then change into a little tyrant - I just can't believe how he sometimes acts & pushes limits, testing me and his father and throwing tantrums!
What I found helpful was to step back and remember that I"M the MOM - and although I'd do anything for my son, I do not have to put up with unacceptable behavior.
He gets a warning to stop the unnacceptable behavior, then if it doesn't stop, I calmly pick him up and carry him to his crib - I tell him that he can come out when he's done with his behavior and says "sorry", and I walk out of the room. He stays there until he stops the tantrum/hollering and then I go get him. The minute it starts again, it's back in the crib. The first time probably lasted a good 40 minutes, and it was hard, but I stuck to my guns.
hope this helps -
J.