* great pay
* great challenges
And in all honesty, I'd say that the former isn't as motivating as you'd think. I've had jobs where I make "plenty enough" money and have quit because I've not been challenged.
In fact, in one in particular I tried to make my own challenges- throwing together concepts and forwarding them to my managers, only to be shot down. Then watch our competitors do exactly what I proposed a few months later. It's demoralising and it made me realise that, as a company, we'd always be on the back foot. I'd never be proud of what I made, and "plenty enough" doesn't make up for that.
So a number of my ideas weren't actually flat out rejected, but they weren't a priority- we already had a list of features to implement. Of course, by the time we implemented those features, the number one had moved on and implemented the stuff I'd originally proposed. Such a frustrating process, and a 100% guarantee that you'll never be the number one company.