Retirement? 70/30 index funds (mix of stock/corp bonds for the 70, short term bonds, tips and money market for the 30).
Emergency fund? Money market.
Other funds? Mix of stock market, credit union account and real estate.
Same as I did for the past 9 years. A diversified mix of Vanguard index funds (with VTI, VXUS and BND being the largest, roughly 70/30 split these days). It might go down like in 2018, it might go up like in 2019, but statistically it will go up. My IRR is ~8%, which is wonderful.
Small sum at say $2-3k? Working from home until Easter, so possibly some cheap tech for a small computer vision, mechatronics, AI lab aimed at reinforcement learning: 3d printer, r&d drone, mini-car, a few robotic arms, plenty of connectors and sensors plus some Raspberry brains.
10% index funds. 90% everything else (this includes ETFs).