The first thing both of my boys grab is their carrots. They each yank their piece out of the bowls and run to seperate hidey's to eat them. Then they come out and eat everything else.
Other favorites (some almost every day, some less often):
Romaine lettuce
Red Leaf lettuce
Raddichio
Cilantro
Grape tomatoes
Bell pepper (any color)
Cucumber
Corn Husks
Kale
Parsley
Veggies They Won't Touch:
Zucchini & Brocolli