Raise/bonus with thanks
I want to take this moment to personally thank you for your valuable contribution to __ (name of firm / name of project) __ . Through the course of your work here, it has not gone unnoticed that your performance has been exemplary and that you have come to be a very valuable member of our team.
Working with you has been a pleasure and I know that we have all come to rely on your expertise. We appreciate your positive outlook and thank you for all your efforts and the commitment you have clearly given to our team.
In appreciation for your hard work and dedication to our company, I am pleased to present you with __ ($__ raise/bonus) __ . On behalf of __ (name of firm)__, we look forward to your lasting tenure of employment with us.