Resets EVE and Adonis campaigns or adds more money on one as the credits stay on them while derezzed. Can also be used during a run to stop ice destruction events from firing (Spooned, Forked, Knifed). Should work best as a one-off for resetting all your money makers in an asset heavy HB or glacier.
Correction: Timing structure is [paid abilities, rez, score] -> [turn starts]. So it would be impossible to fire the card twice. So the paragraph below is false. As it was mentioned in the comments, I'll leave it here.
You could also potentially use it to fire "at the start of your turn" effects multiple times. Early Early Premiere for example. Rez the card, use the effect, rez this, derez that card, rez it again.
(The Universe of Tomorrow era)
Thank you for explaining why I'd want to use this card. It wasn't immediately apparent to me and I had just glossed over this one. The best I came up with was derezzing Chimera to change its type.
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bubbathegoat
Your last paragraph is incorrect for two reasons. First, there is no paid ability window during "start of turn", so you cannot fire Test Grounds. Second, even if you could fire it to derez and re-rez (e.g.) Early Premiere, the second rez would be too late to be triggered by the "start of turn" phase.
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umchoyka
There is a paid ability window before the turn starts, but, yes, it couldn't fire twice. Rezzing, derezzing and paid abilities would happen before the turn starts so you could waste a derez on it, but it would still fire only once (Rulebook - Timing structure of turns).
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tendermovement
You could also (jank alert) derez cheap, early game Draco, so you can make it more relevant later in a game. Or Elizabeth Mills, if that's how you play.
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toiry
It'll help with the upcoming NBN identity as well, which drains runner credits when you rez advertisements.
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Crauseon
You can also derez an ICE that has been parasited, since it has no strength it won't die taking up one of the runners MU and preventing parasite reuse with clonechip or dejavu unless the runner trashes the parasite themself.
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BoomFrog
BoomFrog that's a pretty trollish move. The downside is if it was expensive ice you've got to rez it again after the runner trashes the parasite, for a net profit to the runner.
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Zakalwe