i agree with xant; the left-to-right feint is the easiest to block, and i've always seen it that way.
unfortunately it has become my 'main' feint, so when i don't think about what i'm doing, i automaticly make the left-to-right feint and it gets blocked 199/200 times.
I've experienced that the easiest way to kill bad-medium players is with a sideswing feint followed by overhead attack. many unexperienced players cant block this, and it will also get through some of the more experienced players' blocks (althoguh not that often)
so if you're new, i suggest you try to practice this one.
the double overhead is also fine
another easy and, imo, usefull attack is the held attack. Instead of immediately releasing your attack, hold it for a sec or 2, most players attack by reflex as they know the amount of time it will take your weapon to reach their block, and they think it's their turn to attack, but as your attack is delayed, you hit him while he attacks.