Ableton Live is a software music sequencer and digital audio workstation. Designed to be an instrument for live performances. Very often used by DJs.
+ native 64 bit support
+ great beatmatching, crossfading algorithms for DJ use
+ comes with bunch of predefined synth, samples, drum-kits and loops
+ pack of internal audio effects for audio tweaking
+ supporting great amount of DJ hardware
+ can be easily controlled by Android devices
- not so intuitive interface and ergonomics, i prefer vertical orientated software like Renoise