In my case, it’s a tie between my youngest sister and my best friend from college. They both think highly of me; in fact, I sometimes fear that they think TOO highly of me. I’ve frequently been brought back from the brink of doing foolish, immoral, or self-destructive things because I don’t want to disappoint them.
Anybody else?
I thought about making this an automated poll, but those tend to discourage posting. Also I couldn’t be arsed, what with being lazy.
Wife. IMHO, this comes close to defining what a marriage is fundamentally about: the one person who knows your faults and errors better than anyone is still the one person whose standards they set for you, you try, every day, to live up to (and frequently fail to).
Mr. Ko.
Wife, then students, then fellow coaches.
I am still trying to be like my father because I respected his opinions on a whole lot of things.
Spouse, daughter, sister in law, friends.
I think it’s always about the people whom you respect the most.
My wife of 40 years, my Best Friend, my Reason for Living. All the same person.
Apologies for going all ickysweet, but it’s the truth.
.
My dad’s.
I spent years thinking I could never live up to my dad’s hopes for me. To be honest, he’s not a terribly successful guy, financially-speaking, but he clearly wanted me to do better than he did. After I graduated from college, I didn’t know what I wanted to do, so I moved back home and spent a couple of whiny, angst-filled years working shitty jobs and mooning about how I didn’t have a path in life. He was really disappointed in me and would occasionally try to have heart-to-heart talks about how I had a college degree and did I really want to spend the rest of my life working in a bookstore?
Now I’m finishing up my masters degree and it is ridiculous how pleased he is. I actually don’t know how to handle it, it’s such a new and weird experience.
If I have to move back to my parents’ house in a few months because I can’t find a job, he may change his opinion again.
P.S. Anyone looking to hire a foreign affairs policy analyst?
It used to be my dad’s; then my mom’s. But they’re both dead. I value my friends, and appreciate that they appreciate me. I like that my boss thinks highly of me. I’m good at what I do, and it’s fulfilling to me when I can solve a problem.
When it comes right down to it, it’s my own opinion I value most. There are people who like me, and people who don’t. I comport myself in such a manner as to get along with the former, and I don’t give a rodent’s rectum about the latter. In the end, I have to live with myself.
Quoted for truth. Past my wife, perhaps my father followed by the rest of my family (including the dreaded in-laws, with whom I’m quite close to and fond of - go figure).
My mates/ex colleigues.
My first wife when we were married.
Skald’s
Sorry, what was the question?
Bets on how long before some some kiss-ass with low self-esteem says “You people?” 
My own.
There’s plenty of people I love and whose opinions I value but dammit, I have to look myself in the mirror every day and I want to be able to continue doing that.
Ooh! Ooh! Me me me!
…nah, never mind.
That’s because you’re sane, dear.
It’s my own fault for not specifying “other than yourself,” though.
My boyfriend. He’s the only person I see every day and he knows me better than anyone else does. It’s hard to value the opinion of someone that doesn’t really know you.
Making sure I’m someone he can be proud of helps keep me from doing stupid, lazy things that’d lower my opinion of myself, too.
My husband’s. Because he’s a genuinely good person whose opinion I respect, and because my life would probably be a bit difficult if my husband didn’t approve of me. 
After my husband, my sister. She’s my best friend, and a person I know will always be there for me, no matter what.
In all seriousness:
Don’t worry Skald, post #12 was a joke, I don’t make decisions based on the opinion of a guy in a secret lair. Well, except for the distant relative and one of the siblings, whom I believe are working on secret lairs.