I like "I am Unstopable!"
It is a shout, so it activates instantly, it cannot be stripped or knocked out of like enchantments or stances.
It provides +24AR, prevents knock downs, prevents Cripple and will even remove it if you under it's effects and it can be kept up for 20 of the 30 second recharge for the skill, longer if your /P
Oddly enough, I am Unstopable also has a bug which I had not noticed until I checked wiki as it will stack passed the 2 Armor Rating buff skill cap
http://guildwars.wikia.com/wiki/%22I_Am_Unstoppable!%22
Great Dwarf Armor is also very good
