Writing shellcodes has always been super fun, but some parts are extremely boring and error prone. Focus only on the fun part, and use ShellNoob!

Features:

convert shellcode between different formats (currently supported: asm, bin, hex, obj, exe, C, python, ruby, pretty)
interactive opcode-to-binary conversion (and viceversa) mode. This is useful when you cannot use specific bytes in the shellcode.
resolve syscall numbers and constants (not exactly implemented yet :-))
portable and easily deployable (it only relies on gcc/as/objdump and python). And it just one python file!
in-place development: you run ShellNoob directly on the target architecture!
other options: prepend breakpoint, 32bit/64bit switch.
read from stdin / write to stdout support (use "-" as filename)

download and info:

https://github.com/reyammer/shellnoob