The _t_ locus, which is described in detail in this book by Robert Trivers, is the classic 'outlaw' or 'selfish' gene.
If a heterozygous (single) _t_ allele is present in the paternal mouse, the t locus is evident in sperm 95% of the time. Talk about "Breakin' the Law"! As a locus whose main phenotype seems to be for mitotic cheating, t seems to convey little or no benefit to the other genes by way of helping the host survive. _t/t_ homozygotes are sterile. Nice summary here.