Spawn a shell:

python -c 'import pty; pty.spawn("/bin/sh")'
echo os.system('/bin/bash')
/bin/sh -i
perl —e 'exec "/bin/sh";'
perl: exec "/bin/sh";
ruby: exec "/bin/sh"
lua: os.execute('/bin/sh')
exec "/bin/sh"

VIM: 
:!bash
:set shell=/bin/bash:shell

nmap:
!sh