Every minute I spend with my kids.

Besides that, I invested 300 bucks in 2008 to register a business and get some accounting software. 14 years later that business had reached 2M/yr revenue at its peak and last year I sold it (sadly not a its peak due to getting rekt in pandemic but I did ok). That was definitely not a passive investment but certainly my biggest financial gain.

The best investment I have made in myself was quitting drinking almost 9 years ago.