Financial Misstatements
Here's the biggest offenders I see when talking to founders:  revenue vs GMV
  (if you give GMV, give me your cut/margin)
  contract vs LOI
  burn vs expenses
  users vs customers 
  (customers pay)
  signups vs users vs active users
  (you should give active with time interval and measurement of active. 
   eg. logged in last 30 days)
  profitable vs cash flow positive

Others people should know:  diff between retention rate vs churn rate
  (both should be given with time interval. 
   eg. 30 day retention rate is...
       monthly churn rate is...)
  voluntary churn vs involuntary churn
  gross vs net
  top line vs bottom line