In the early days, Vanguard was known to have mutual funds with very low
expenses. Nowadays, there are many more low cost options including mutual
funds from other vendors and ETFs.
One thing that's still relatively unique about a Vanguard mutual fund is
that it has more fund classes than its peers.The more investment you make
the lower the cost; but usually you wouldn't get access to the top tier
classes through a retail account. Check out other vendors too, like Fidelity
, etc.