18. Aemilian (3 months in 253) - he was commander of the Danube troops, and was acclaimed Emperor by his army, defeating Gallus... before being killed by his own men (in a shocking twist!) when Valerian proclaimed himself emperor and moved against him. Eutropius' summary of him is beautifully bitchy: "Aemilianus came from an extremely insignificant family, his reign was even more insignificant, and he was slain in the third month."

19. Valerian I (253-260) - Valerian came from a senatorial family, and was consul in 238, and negotiated with Gordian I for senatorial acknowledgement for his claim of emperor. He was marching to help quell Aemillian's revolt when first Gallus' troops murdered him, then Aemillian's troops murdered *him* (I am not kidding when I say this may be the most common cause of death for Barracks Emperors). He was defeated at the battle of Edessa in 260 by Shapur I... and then, during negotiations, taken prisoner and held for the rest of his life, however long that was. In one version, he was skinned and his skin stuffed with straw and held as a trophy - in another, he was forced to swallow molten gold, and in yet another was flayed alive. 

20. Gallienus (253-268) - Valerian's son, Gallienus is notable amongst the barracks emperors for surviving as co-emperor and sole ruler for *more then a decade*. That's pretty impressive. This is a pretty crummy time for the Roman Empire, though - it sees Britain, Spain, parts of Germania and large bits of Gaul break off to form the Gallic Empire (which survived until 274) under the general Postumus, as well as the loss of Palmyra - and numerous other minor rebellions, famine, and plagues. He was... oh, would you look at that. Assassinated by his advisers. 

21. Ingenuus (June 260) - leader of a brief revolt after Valerian I's capture, defeated by Gallienus' general Aureolus. Drowned himself in a river to avoid capture.

22. Regalianus (260) - Elected Emperor by by the Pannonians to deal with the Sarmatians. Shortly afterwards was killed by a coalition of his own people and the Roxoloni. 

23. Macrianus Minor (259/60 - 261) - His father, Macrianus Major, took Valerian's treasury and used that influence to have he and his brother nominated emperors. Was defeated in Thrace in 261 by Aureolus, and asked the legions to kill himself and his father rather then be delivered to him. 

24. Quietus (260-1) - Lost control of his provinces after his father and brother's death to Odaenathus of Palmyra, and was killed by the inhabitants of Emesa whilst it was besieged. 

25. Mussius Aemilianus (261/2) - Supported Macrinus' rebellion, possibly had himself proclaimed emperor after their fall. Was strangled in prison after being captured.