A laser has been developed on the basis of the CW CO2 laser with DC pumping and cross gas flow. An optical resonator of the laser has been developed on the SFUR (Self Filtering Unstable Resonator) scheme. High beam quality is provided by this scheme (full angle divergence is 0,7 mrad on 0,86 power level at beam diameter 30 mm). The laser generates 3 kW output power without any additional equipment. Besides, it is equipped by four accessory units in a feedback arm to provide a variety of operating modes. (1) Single-frequency CW mode with capability of monotone line tuning in bands 9,4 microns and 10,4 microns (about 70 lines in all) with maximum output power up to 2,6 kW at line 10P20 and per-unit frequency instability of the order of 10 to the minus 7th. As it has been shown, there is a possibility to reduce a laser line width to 50 kHz. (2) A mode with rapid tuning of the generation line (with about 1 microsec transition time) in combination with an opportunity to form any given spectral-temporal sequence. The generation spectrum and output power are the same, as in mode 1. (3) Repetition-rate Q-switching mode with high peak power (up to 800 kW) and the average one (up to 2,8 kW) with pulse repetition rate control in the range of 1 - 100 kHz. (4) The repetition-rate Q-switching mode in combination with line-tuning (such as in mode 1) has been developed for selective photochemistry and laser isotope separation. The results of the applications of the laser with repetition rate mode to producing of a new variety of gas discharge-powerful optical pulsating discharge are presented.