The 4017 is pure nostalgia to me - a long long time ago I built a 6-decade counter using 4017's and ten LEDs per decade (rather like a dekatron circuit!) - it could run as a timer (using discrete 1MHz CMOS Xtal oscillator circuit) and possibly a frequency counter as well. In those days LEDs were not bright at all (not visible in daylight when driven from 4017's). IIRC the 4017 has an interestingly random pinout and interestingly random state on power up (more than one output active).