I have to vote for the auto as my favorite opening method. I think it is just really cool, easy to do, and very practical. Of course it is illegal almost everywhere.
My next vote would be for balisong, as it also has a high marks for cool opening/closing factor. Of course it requires considerable skill, and practice. I also feel it is not a very useful type of knife for daily carry.
My favorite type of knife or EDC is ofcourse just a thumstud/hole type one hand opener. It is very practical, and legal just about everywhere. In this catagory I must say the best method is assisted openening, some of the toy factor of a switchblade, and the legality of a one hand knife.
Erik