EDB (Evan's Debugger)!

The IDA Pro Disassembler and debugger is a multi-processor disassembler and debugger hosted on the Windows, Linux and Mac OS X Platforms.

OllyDbg is a 32-bit assembler level analysing debugger. Emphasis on binary code analysis makes it particularly useful in cases where source is unavailable.

x64_dbg is a 32-bit and 64-bit assembler level debugger for Windows.

GNU Project Debugger, or gdb, is a command-line, source-level debugger for programs that were written in C, C++, D, Objective-C, Fortran, Java, Pascal, assembly, Modula-2, or Ada and compiled for any of a number of different target architectures including x86, x86-64, IA-64, Alpha, ARM, Motorola 68000, MIPS, PowerPC, SPARC, and others. gdb supports hardware breakpoints, conditions, core dump analysis, expression evaluation, remote debugging, stepping into/out of code, disassembling, and, in some cases, reversible debugging. »

Bokken is a GUI for the Pyew and Radare projects so it offers almost all the same features that Pyew has and and some of the Radare's ones. It's intended to be a basic disassembler, mainly, to analyze malware and vulnerabilities.

Immunity Debugger is a powerful new way to write exploits, analyze malware, and reverse engineer binary files. It builds on a solid user interface with function graphing, the industrys first heap analysis tool built specifically for heap creation, and a large and well supported Python API for easy extensibility.

A general, open source, retargetable decompiler of machine code programs

ArkDasm is a 64-bit interactive disassembler and debugger for Windows.

ODA is an online disassembler for a wide range of machine architectures, including: Alpha, ARM, AVR, Intel x86, Motorola 68000, MIPS, PDP-11, PowerPC, SPARC, Z80, and more! Upload a Windows PE file, ELF, or raw binary and then view the disassembly and object file meta date such as symbols and sections.