While there is a thread around here polling *bad * things to say to kids, I thought we ought to remind each other of *good * things.
When I was a teenager, my dad was away somewhere and we were talking on the phone. Before we said goodbye he said:
“Hey! I’ve been bragging about you!”
I’ve never forgotten that.
“I believe you, and I’m going to help you.”
“You are a wonderful person and I like spending time with you.”
“Wow! What a great job you did!”
“I’m so proud of you!”
“I love you no matter what.”
“Here’s the keys to the car and fifty bucks and don’t worry about your homework or chores, I did it all for you. See you whenever you get home!” Well, okay, maybe from the kid’s point of view. 
“Let’s go get ice cream!” (or go out for dinner)
“You know, I’m really glad you’re my kid!”
“I love you”, which I say daily to my little ones (ages 3 and 6)
“You’re the best thing that ever happened to me.”
“I’m too tired to beat you tonight.”
Just kidding.
I’d also like to point out that real child abuse isn’t funny, I just thought it was an amusing juxtaposition.
“Ninety percent of everything is crap. That applies to conversations, to things you buy, to the things you need to do, to the things you learn in school, to the People you meet, to the Secrets of the Universe. Keep that in mind as you grow up.”
“Everybody in the world is going to tell you that you’re supposed to be like them, to talk like them, to act like them. They’re wrong. Be You, not them.”
“I love you.”
Everything else is pretty much window dressing. (Not that window dressing is so very bad, mind you.)
When my pops calls sometimes he’ll say: “I just wanted to hear your voice son”
“Don’t tell your brothers and sisters, but you really are my favorite” 
Optimist.
Wow
Way to Go
Super
You’r Special
Outstanding
Excellent
Great
Good
Neat
Well Done
Remarkable
I knew you could Do it
I’m Proud of You
Fantastic
Supper Star
Nice Work
Looking Good
You’re on top of it
Beautiful
Now You’re Flying
You’re Catching On
Now You’ve Got it
You’re Incredible
Bravo
You’re Fantastic
Hurray For You
You’re on Target
You’re on Your way
How nice
How Smart
Good Job
That’s incredible*
Hot Dog
Dynamite
You’re Beautiful
You’re Unique
Nothing can Stop You Now
Good for You
I like you
You’re a Winner
Remarkable Job
Beautiful work
Spectacular
You’re Spectacular
You’re Darling
You’re Precious
Great Discovery
You’ve Discovered the Secret
You Figured it out
Fantastic Job
Hip, Hip, Hurray
Bingo
Magnificent
Marvelous
Terrific
You’re important
Phenomenal
You’re sensational
Super Work
Creative Job
Super Job
Fantastic Job
Exceptional performance
You’re a Real Trooper
You are Responsible
You Are Exciting
You Learned it Right
What an Imagination
What a Good Listener
You are Fun
You’re Growing up
You Tried Hard
You Care
Beautiful Sharing
Outstanding Performance
You’re a Good Friend
I Trust You
You’re important
You Mean A Lot to Me
You make me Happy
You Belong
You’ve Got a friend
You make me Laugh
You Brighten My Day
I respect you
You Mean the World to me
That’s Correct
You’re a Joy
You’re a Treasure*
You’re Wonderful
You’re Perfect
Awesome A+ Job
You’re A-OK
My Buddy
You Made My Day
That’s The Best
A Big Hug
A Big Kiss
I Love You
Also it should be noted that tone of voice and body language are impoortant in the delivery of many of these. Complimentary words can be said quite easily in a manner that is more damaging than complimentary.
I really like Roadwalker and Tony Montana’s. Going to remember them to use if the opportunity presents itself.
“You’re going to be OK”
Invaluable advice from my dad, “Pops” Mercotan.
“Never turn down anything that’s free.”
Honestly, that’s the best thing my dad ever told me.
Mmm… Supper star…
“I always dreamed I’d have a son/daughter just like you”
Julie
“It is impossible to overestimate how important a good reputation is. This applies to getting a job, getting a loan, and getting a girlfriend. Maintain your reputation at a high level, no matter the cost.”
“Always listen to your instincts. If they say ‘this person is full of shit,’ then they are.”
“Son (or daughter), I’m as proud of how hard you tried than I am of whether you ultimately won or lost. There is no shame in losing if you know you did all you could.”
“You are such a neat kid! I’m so glad you’re mine!”
Is it any wonder my mom is one of my best friends?
Go mow the lawn.
“I’d love to (do something) with you.”
I also thought immediately of zev_steinhardt’s wonderful post about his children as just chock full of good things to say to your kids.