The quantum mechanical behavior of light nuclei (such as hydrogen) can have a dramatic effect on physical properties of condensed phase systems. For instance, one can extrapolate the pH of isotopically pure waters to the infinite-mass limit, and estimate that a 'classical' water would have pH=8.5. An appropriate GLE can enforce a phase-space distribution consistent with a quantum harmonic oscillator without any significant overhead. This allows one to model nuclear quantum effects in a classical simulation inexpensively. A systematic improvement of the accuracy in strongly anharmonic problems can be achieved by combining this approach with path integral molecular dynamics (with a much lower number of replicas than for a fully converged PI simulation).