Having been in a similar situation about 6 months ago I am sorry to tell you that; the magical idea will never show up one day.

Have you ever worked in the enterprise? If so, what would YOU love to see changed?

If you come up with any idea you can run it against this checklist:

1) Does it replace something that people use today? If Yes, you need to look at every integration point of this service and provide a seamless transition (Not easy)
2) Try to cater to fixing a single problem that is cross-cutting across departments (if only sales or HR can use it, you are in the vertical domain knowledge business. That is hard to establish yourself in. Instead stick with a wide problem -- Look at WuFoo for example)
3) Make sure whatever you provide has immediate, measurable value proposition. E.g; Create forms without relying on your IT team, track time 4x faster than using Excel etc.

If you want to bounce your ideas off of me, I would be happy to help.