What's the one thing Ableton has vs other DAWS that you can't live without ?

For me it's the LFO tool and the way you can map it to just about anything. Turns Ableton into a full on Modular Synth sometimes the day I saw that I knew this was gonna be my instrument.

That and the Audio from Resampling feature and the way it allows you to record from master in real time how you would on a sampler. You can go into really deep sound design territory on the session view using it and no other DAW I've used quite has given me that level of freedom.