Cubase 4 as the main work horse used Cubase since Atari days and just don't feel as comfortable sequencing on anything else and for my money this is the best version of it so far certainly blows away all the SX versions.
Ableton 7 for playing live and more and more often dj'ing with also. use it for when I'm recording from Analog like RDR and for when I'm sampling from records handles audio in a far more intuative way than anything else I have used.
Reason 4 just started using this for Thor basically probably the best thought out softsynth I have seen in a while. Always thought Reason was a bit shit in the past I have to say this version has proved me wrong.
Logic 8 Occasionally I use this but being a die hard Cubase man I really struggle to come to grips with it .Straight out of the box this has the best sounding plugs and softsynths of all of them though.
Melodyne 3 I essentially only use this for extreme pitching etc so a bit of a waste really as it's an absolute monster if you can be bothered to get under the skin of it.