Measurements of basal plane longitudinal ρb(B) and Hall ρH(B) resistivities were performed on highly oriented pyrolytic graphite samples in a pulsed magnetic field up to B=50T applied perpendicular to graphene planes, and temperatures 1.5K≤T≤4.2K. At B>30T and for all studied samples, we observed a sign change in ρH(B) from electron- to holelike. For our best quality sample, the measurements revealed the enhancement in ρb(B) for B>34T (T=1.8K), presumably associated with the field-driven charge density wave or Wigner crystallization transition. In addition, well-defined plateaus in ρH(B) were detected in the ultraquantum limit revealing possible signatures of the fractional quantum Hall effect in graphite. © 2009 The American Physical Society.