To kick things off - check out some of the things fellow Causal users have been sharing on Twitter 
- Simple SaaS model
- Recurring liquidity compensation calculator
- Basic cohort modelling
- Venture fund modelling
- Paid search forecaster
- Convertible notes
- 3 statement model (using Tesla as an example)
- Customizable calculators: Tended, Pokt, Flow’s take on choosing healthcare providers/plans
- Personal finance: Buy vs Rent, Student Loan Repayment