General Tools

first of all, you will need cheat engine. duh.
http://cheatengine.org/
(if you cant see the big green download button, just stop here. seriously. stop while youre ahead)

and charles web debugging proxy is useful sometimes
http://www.charlesproxy.com/

kadat's recommended hex editor "010 Editor - If you arent using this hex editor, you're doing it wrong."
http://www.sweetscape.com/010editor/

kadat's Kongregate Badge Hack, yes that's right KBH is back, use this to award badges on Kongregate
note: the KBH is now integrated into the ultra trainer.
https://konghack.com/topic/8871-konghack_ultra_trainer

Want to make your own trainer for flash games? well now you can with dudial's easy trainer creator
http://konghack.com/view_topic.php?t=8172

Flash Stuff

and kadat's swf dumper is great.
http://gcw.cz/SWFDumper

and dont forget his raw data extractor as well
http://gcw.cz/RawAoB
 

SWF Decrypt to decrypt as3. UnSWFEncryptUNP for as2
http://konghack.com/files/000000000040/files/swfDecrypt.zip

then to make AoB's sothink is a must
http://www.sothink.com/product/flashdecompiler/

and an swf comp/decomp if you need one for some reason
http://swf-compressor.en.lo4d.com/download

and a .sol save file editor because thats always nice
http://blog.coursevector.com/minerva
http://sourceforge.net/projects/soleditor/ *
*outdated, but it has the useful function of adding booleans and such. ...if it can read the sol

Unity stuff

lht's unity dumper.
download http://www.sendspace.com/file/qiyu9c
forum link http://konghack.com/view_topic.php?tid=9647369

and kadat's swf dumper. again. its multi-purpose!
http://gcw.cz/SWFDumper
 

.NET reflector - decompile .net applications (sothink for unity)
http://www.red-gate.com/products/dotnet-development/reflector/

Gray Wolf - (free alternative to redgate's reflector) focuses more on attacking .net applications
Note - Although im sure its safe, I havent personally checked that this doesnt contain malware, but it does work quite well and will dogfood so it's probably safe ~ KolonelKadat
http://www.digitalbodyguard.com/graywolf.html

Simple Assembly Explorer - Free opensource .NET decompiler
https://sites.google.com/site/simpledotnet/simple-assembly-explorer
https://sites.google.com/site/simpledotnet/simple-assembly-explorer/SAE.v1.14.4.x86.7z?attredirects=0&d=1
https://sites.google.com/site/simpledotnet/simple-assembly-explorer/SAE.v1.14.4.x64.7z?attredirects=0&d=1
 

Edit by Thenewcomer: added some things. thanks gates
Edit by VxD: added kadat's KBH and dudial's trainer creator
Edit by gates: added SAE
 

Here are two files, swfcomp.exe and swfdecomp.exe.

If your .swf is compressed, just drag it to swfdecomp.exe and it will decompress it for you.
If you want to compress your .swf, just drag it to swfcomp.exe and it will compress it for you.

How do you know if your .swf is compressed or decompressed? Open it in a hex editor and look at the first 3 bytes. They will either be: 43 57 53 - CWS or 46 57 53 - FWS. CWS is compressed and FWS is decompressed. When looking for AoBs you will want to make sure that your .swf is decompressed.

Note: When using kolonelkadat's SWF Memory Dumper, you will be dumping the .swf from memory where it is already decompressed. The decompressor comes in handy when you are downloading the .swfs directly from websites.

 

Since I can't double post....

Here are two more that people can't seem to find:   UnSWFEncryptUNP and SWF Decrypt