This is a small size LED flasher, operating from 3V. It may be useful as a flashing metronome, memo-reminder or in any other similar application.
The circuit is an astable multivibrator with a duty circle of about 10%. The LED will be on for a short period and off for a longer period, during every cycle.The duty circle is intentionally kept low to ensure low power consumption.
You may use any other power supply voltage, up to 12V, but you must change the value of R3 accordingly.