Hey I am new to this site, and was wondering what people on here use to design games. I'm currently using Unity3d and love it!
i use pen and paper to design games.
to build the games themselves, i don't use an engine, i use directx 9.0 (for the moment), in-house "game parts" libraries, c code, and MS C++ 2012 express compiler.
i use TrueSpace 7.61 beta for modeling, TrueSpace 7.6 for converting model formats, paint.net, and free clone stamp tool. i have an in-house rigid body modeling and animation system with model and animation databases and an animation manager in one library [EDIT: the "game parts" library], and a model and animation editor in a second library [EDIT: the "modeler" library]. they both use the in-house mesh, texture, and material databases in the "game parts" library.
for audio, in the past i've, used winjammer midi sequencer. but most of my game music is original stuff, loop based wav's, drums, guitar, bass, etc sampled into the PC. its played through an in-house loop based wav music player. despite having sound forge etc. i find a simple wav editor is all that's needed to mix the loops. in the past, sound has been based off of directsound, but this time around it looks like i'll be using the xaudio2 api.
as you can see, your use of the phrase "what people use to design games" when you probably meant "what engine people use to build games" will not exactly get you the response you expected <g>.
folks here are rather literal minded, and rightly so. game development is a technical endeavor warranting precise terminology.
in game development, the tasks might be broadly described as: design, code, artwork, other content creation, music/sfx, marketing, and admin. slicing the world that way, unity is primarily a code engine / runtime module combined with content creation tools. modifying the unity engine would be considered code work. simply using it to create games would be considered primarily "additional content creation" - IE level design. using its scripting capabilities to extend the engine would probably be considered code work.
its the fact that design is one aspect of development, and the fact that you used the term "design" when you probably meant "development" that may lead to a little confusion.
unless you really did want to know that most designers used paper and pen or the software equivalent thereof (word processor, spreadsheet, database, and graphics programs). <g>.