IT bonuses

I took a new position and discussed using a bonus structure tied to projects and the like. This company is very bonus driven and liked my ideas, so now they asked me what I had in mind and to come up with some bonus ideas. So what type of IT bonuses (project or other) has anyone used or heard off. I want to maximize my return while being fair. I have a lot of projects going on and currently the only IT person in their employ. Also, I am underpaid but aren’t we all.

What kind of ideas or experiences does anyone have?

Thanks