Conventional wisdom has it that ubiquitin ligases (E3s) and deubiquitinases (DUBs) have very different activities, with the former modifying substrates with ubiquitin presented by dedicated E2s, and the latter hydrolyzing (iso-)peptide bonds from the C-terminus of ubiquitin. Recently, we described the unconventional bacterial ubiquitin C-terminal clippases (UCCs), which cleave peptide bonds within the C-terminus of ubiquitin, amounting to a 'destructive deubiquitination'. Here, we present several new families of bacterial effectors that combine aspects of both E3 and DUB activities. When viewed through an E3 lens, these enzymes can function as rather conventional E2-dependent cysteine-relay ligases, although they do not belong to any known E3 class. Unlike other ligases, they can also utilize ubiquitin that is not presented by E2s, but rather appropriated from a pre-existing ubiquitin chain or ubiquitinated substrate. This type of activity, which allows the enzyme to function even after exhaustion of ATP or free ubiquitin pools, can be considered a 'klepto-ligase'. Conversely, when viewed through a DUB lens, this type of activity would allow the effector-encoding bacterium to get rid of an undesirable ubiquitination – e.g. from the bacterial surface – and simultaneously transfer the removed ubiquitin to other targets in a 'transubiquitinase' (TUB) reaction. At the molecular level, these enzymes resemble a new class of cysteine proteases with a Cys-His-Asp active site, which surprisingly was also found to be essential for the canonical E2-dependent ligase activity.