Generally Muntjac will only fight with their teeth. This may be because they bread all year round and therefore are without antlers capable of use in a rutting or territory fight for around half of the year.
However as they cannot read I am sure that someone will see them using their antlers.
Extracted from Charles Smith-Jones excellent study of muntjac:
"The bucks will engage in a shoving match using antlers, pedicles and foreheads, each pushing and twisting in an attempt to throw their opponent off balance. The buck that succeeds in doing this will then attempt to slash his adversary with his tusks, aiming for face, ears or neck...or rump, in the case of a fleeing opponent."
This tallies with what I have seen of muntjac - mostly there's a lot of 'foreplay' as they opponents stamp and stare. Only if this fails will you get physical confrontation but I've not seen anything other than the above.
I fully agree with the above - why would a deer bother wasting precious energy in growing antlers that would otherwise be pointless?
willie_gunn makes an excellent point as well - the foreplay is part of sizing each other up, and can include parallel walking. If one buck is clearly weaker they won't even bother coming to blows - he'll back down if faced with the certainty of being beaten.