I have moved on to my own business at this time with coaching and training, however in my previous positions, servant leadership tended to be the best reward for my employees. 

I took a position upon returning from overseas with a new team who I was told had the lowest employee survey score of the company (Welcome back :)). 

I took my time meeting with each employee, listening and understanding where they were in most areas of life, coached them so they discovered solutions they could live with or move them forward, then I did daily walk arounds to touch base with as many of them as I could and talked about what they wanted to talk about....family, work, interests, etc. In 2 years, my teams scores went from the low 30's on average, out of 100, to an average of 85+.

While we had several other in encentives, and I gave those out when I could, this get-close-and-personal approach worked the best, I believe it developed intrinsic motivation versus the extrinsic material benefits and so the impacts were greater. 

Oh, and this was all during a 2 year downturn in our industry, major changes in job requirments and addtional layoffs. 

Not looking to brag but really, the company I worked for for almost 20 years had all kinds of employee improvement plans and incentives, but after 10 years of leadership, servant leadership gave me the greatest return on investment.