We study the deviations induced on the global HI 21 cm signal from the Dark Ages to Cosmic Reionization by some popular annihilating Dark Matter (DM) candidates: (i) a 10 GeV Bino-like neutralino (ii) a 200 GeV Wino and (iii) a 1 TeV heavier particle annihilating into leptons. Their choice is motivated by hints of direct/indirect DM detection from a number of recent observations and each DM model is in agreement with CMB observations by WMAP. We use our Monte Carlo scheme MEDEA2 to calculate the fractional energy depositions for each DM candidate and therefore we are able to compute the DM-induced deviations on the IGM thermal and ionization history and consequently on the HI 21 cm line. Moreover, for the first time in such studies, we include heating and ionization by galaxies to investigate ways to disentangle the DM imprint on the IGM via redshifted HI 21 cm line observations. We find that including luminous sources actually increases the DM signal, which could be detected by futu re radio interferometers assuming that a number of observational difficulties can be addressed, representing a clear proof of energy injection by DM at high redshifts. Finally we highlight the possibility of detecting a clean trace of DM annihilations by a study of the gradient with frequency of the HI 21 cm line.