I have a slightly off-label use for Rapportive that's given me incredible value: I use it to guess email addresses by trying common formats until one works (e.g. first@company.com, first.last@company.com, flast@company.com, etc.). Nine times out of 10 it works, and it's one of the best sales tools there is.

How about making this a real feature, or its own app? Maybe a form where I can type in as much as I know about someone, and the app can automate the guessing process (including company email addresses and common structures for personal emails) until it finds a result? I would probably pay for that.