Seeing how the Pacers are far from being a playoff caliber team, I wouldn't trade for anyone older than him. So using that criteria, I would go after one of the following:

Lebron James
Chris Paul
Dwight Howard
Brandon Roy
Josh Smith
Andrew Bynum
Deron Williams
Chris Bosh
Al Jefferson

What people don't realize is that Danny isn't even that young for this league--his current age of 25 yrs makes him only one year younger than the average NBA player. Sure, he's having a break out season, but almost every 2/3 reaches a similar offensive peak at that age! Michael Jordan, Reggie Miller, Paul Pierce, Tracy McGrady, and Joe Johnson are a few examples. Just look at the numbers and you'll see that a lot of these guys have career scoring years at that age. I'm not knocking Danny, I just think his future value may be a little inflated based on how he is performing now, and while he will be a star player for many years to come he probably won't top this season. That's why I would ONLY trade him for a younger player who hasn't reached his zenith yet.