I believe ABC, one of python's influence, used tagged pointers, but I can't find a quote on this. Not using tagged pointers was a conscientious decision from Guido (see e.g. https://github.com/dropbox/pyston/issues/181#issuecomment-62...)

[edited] Something that people often overlook when talking about optimizing python is that the "simplicity" of the C Python API allowed the rich ecosystem of C extensions. GC, tagged pointers, etc... are great, and often used in modern VMs, but they tend to make integration w/ C code more difficult. Without rich C extensions, no numpy, no scipy, no scikit learn, no tensorflow/theano/etc... I am not sure this is completely incidental.

[edit 2] Ah, found the quote I remembered about tagged pointers in ABC from Guido: https://mail.python.org/pipermail/python-dev/2004-July/04614...