Catalyzes the hydrolysis of nucleoside triphosphates including dGTP, dTTP, dCTP, their oxidized forms like 8-oxo-dGTP and the prodrug thiopurine derivatives 6-thio-dGTP and 6-thio-GTP (PubMed:26238318). Could also catalyze the hydrolysis of some nucleoside diphosphate derivatives (PubMed:22556419, PubMed:26238318). Hydrolyzes oxidized nucleosides triphosphates like 8-oxo-dGTP in vitro, but the specificity and efficiency towards these substrates are low. Therefore, the potential in vivo sanitizing role of this enzyme, that would consist in removing oxidatively damaged forms of nucleosides to prevent their incorporation into DNA, is unclear (PubMed:22556419, PubMed:26238318). Through the hydrolysis of thioguanosine triphosphates may participate in the catabolism of thiopurine drugs (PubMed:25108385, PubMed:26238318). May also have a role in DNA synthesis and cell cycle progression by stabilizing PCNA (PubMed:19419956). Exhibits decapping activity towards dpCoA-capped RNAs in vitro (By similarity). In vitro, it catalyzes the hydrolysis of isoprene pyrophosphates, including (2E)- geranyl diphosphate, isopentenyl diphosphate, (2E,6E)-farnesyl diphosphate and dimethylallyl diphosphate (PubMed:38944687). It may therefore play a role in the control of cellular levels of these metabolites that are essential for multiple cellular processes, including isoprenoids synthesis and protein isoprenylation (Probable). {ECO:0000250|UniProtKB:Q8BG93, ECO:0000269|PubMed:19419956, ECO:0000269|PubMed:22556419, ECO:0000269|PubMed:25108385, ECO:0000269|PubMed:26238318, ECO:0000269|PubMed:38944687, ECO:0000305|PubMed:38944687}. This is the function of NUDT15 (nudix hydrolase 15, ENSG00000136159).