Claws of Gix
Diamond Valley
Grave Pact
Isochron Scepter
Kokusho, the Evening Star
Lifeline
Stifle
Lifeline lets creatures that go to the GY come back at end of turn, but there has to be another creature in play (maybe darksteel colossus?)
Kokusho has go to gy ability that makes your opponents lose 5 life and you gain life that is lost that way (in a 1 on 1 duel it's 5 life for you and -5 for your opponent)
Claws and Diamond valley lets you sac the Kokusho, lifeline brings it back.
Stifle and scepter let you stop your opponent from doing it once per turn.
Grave pact m,ay not be so good, since they just get their creatures back at EOT, but it could be used to keep them from attacking since it's at EOT.