Here are the classes, structs, unions and interfaces with brief descriptions:

CAverageFissionHeat
CCammiFuel
CCammiModerator
CConservativeAdvectionNoBCBC
CConstantDifferenceAux
CConvectiveHeatExchanger
CCoupledFissionKernel
CCoupledOutflowBC
CCoupledScalarAdvection
CCoupledScalarAdvectionNoBCBC
CDecayHeatSource
CDelayedNeutronSource
CDGTurbulentDiffusion
CDiffusionNoBCBC
CDiracHX
CDivFreeCoupledScalarAdvection
CDivisionPostprocessor
CElementL2Diff
CElmIntegTotFissHeatPostprocessor
CElmIntegTotFissNtsPostprocessor
CElmIntegTotFissPostprocessor
CFissionHeatSource
CFissionHeatSourceAux
CFissionHeatSourceTransientAux
CGammaHeatSource
CGenericMoltresMaterial
CGraphiteTwoGrpXSFunctionMaterial
CGroupDiffusion
CHeatPrecursorDecay
CHeatPrecursorSource
CINSADEnergyTurbulentDiffusion
CINSADMassPSPGBC
CINSADMomentumSUPGBC
CINSADMomentumTurbulentNoBCBC
CINSADMomentumTurbulentViscous
CINSBoussinesqBodyForce
CInScatter
CIntegralNewVariablePostprocessor
CIntegralOldVariablePostprocessor
CLimitK
CLinLogPenaltyDirichletBC
CMatDiffusionAux
CMatDiffusionFluxBC
CModeratorHeatSourceTransientAux
CMoltresApp
CMoltresJsonMaterial
CMsreFuelTwoGrpXSFunctionMaterial
CNeutronLeakage
CNtAction
CNtTimeDerivative
CNuclearMaterial
CNusselt
CPostprocessorCoupledInflowBC
CPrecursorAction
CPrecursorDecay
CPrecursorSource
CRoddedMaterial
CSATauMaterialTempl
CSATauStabilized3Eqn
CSATimeDerivative
CSATurbulentViscosity
CSATurbulentViscosityAux
CSATurbulentViscosityNoBCBC
CSATurbulentViscositySUPG
CSATurbulentViscositySUPGBC
CScalarAdvectionArtDiff
CScalarAdvectionArtDiffNoBCBC
CScalarTransportBase
CScalarTransportTimeDerivative
CSideWeightedIntegralPostprocessor
CSigmaR
CTotalNeutronLeakage
CTransientFissionHeatSource
CTurbulentStressAux
CVacuumConcBC
CVariableNotAMooseObjectAction
CWallDistanceAux
CWallShearStressAux