On the Sharp PC-1211 pocket computer (also rebranded as TRS-80 PC1 and as variants PC-1210/PC-1212) you could omit the LET keyword for simple assignments but you were required to use it in an IF statement as there was no THEN keyword (and no ELSE obviously) which would require a keyword to mark the end of boolean expression.

    10: A=1
    20: IF B=10LET A=2:GOTO 40
    30: PRINT "A*B=";AB: REM * as multiplication was also optional
    40: END

Later models based on the SC61860 ESR-H cpu (PC-12??, PC-13?0, PC-14??, etc.) added the THEN keyword but still required the LET after the THEN but only there.