Carrots are probably the #1 thing that comes to mind. However, our horses eat most garden produce. They tend to snatch things out of the chicken's bucket when I set it down to open the door to the henhouse, so I have learned to toss a few squash, cucumber, turnips, or whatever out to the horses on my way to the henhouse, or I'll likely get mobbed.
Their favorite summer treat is watermelon rind. They don't care how well it's cleaned, either. The grandkids will often leave a lot of the "good part" on the rind because they are in a hurry to get another piece before it's all gone. It's hilarious watching the horses eat the rinds, with all that juice running out of their mouths and the look of bliss on their faces! (You have to be careful, though - too much of a good thing can lead to colic.)
Plain Old Dee, horses Dancer and Rain I believe in dragons, unicorns, good men and other mythical creatures!