Parent trick #10: COME HERE!

A child knows the difference between the come-here-because-you-need-to-pick-up-your-toys tone and the one that says, "Hey! Let's go get ice cream!" Sometimes I like to use the latter even if it is the first one.

They will be more responsive to your call if it doesn't necessarily mean they are in trouble. Call them over just to give them a big hug and tell them how much you love them. Watch them glow.
...Or watch them be annoyed that you interrupted their playing. :) Children can be pretty unpredictable, but it's worth trying. 

Try this:
"Hey, Merv, look." Put out both hands in fists for him to see. "Pick a hand." What kid isn't going to respond to that? Have some little prize in one (ie: a dime, a couple jelly beans, etc). If it's just a spur of the moment thing like they don't want to come to you when you are trying to get out the door, you can still use the "pick a hand" trick. When they have tried each hand you could cup their little face in your hands and smother them with kisses. Proceed to put on their shoes and head out the door.