Environment

[Grabnor]

I use Notepad++, with pseudo-intellisense.

Shameless plug:

Rift Lua autocomplete for Notepad++

[Sunspots]

I've actually gone over to IDEA with Lua plugin, with Rift API support...
Not sure if the Notepad++ handles functions with colons in a good manner (I don't want, for example, SetVisible() to come up all the time, unless it's after a colon (and even more preferably if it could learn that a variable contains a UI element, and even better if it knew what type))

[doxxx]

IDEA with Lua plugin. I use it all the time for Java stuff, so I'm used to it.

[BuGi]

Notepad++ with rift autocomplete