I am easily able to fix the one with Shaco's clone killing Kog'Maw, but apparently there is at least one other one sneaking around out there somewhere. If you have seen any instances that do NOT involve Shaco's clone killing Kog'maw, and getting 2 deaths, please try to list any information you have, such as:
Enemy team's champions and who got the double kill
Applicable buffs/etc used/had (examples Lizard, Nashor, etc)
Description of the double kill - how it occurred. So far there are 3 known issues of how this can bug:
1) Champion with 'zombie mode' effect (Kog'maw, Karthus, or anyone with Yorick ult on them) dies and then immediately dies again, never going into the zombie mode effect. Seems to be only seen on Yorick as far as I know. I have a fix for this version of the bug, provided it only exists on Yorick.
2) Champion with 'zombie mode' effect dies and then somehow dies again right at the end. Seen a screenshot in another thread of Karthus killing a zombie Kog'maw at the end. Have no repro information for this version of the bug.
2) Champion with 'zombie mode' effect dies, goes into the effect of their zombie mode, and then at the end dies again. Easily reproducable with Shaco, but might also occur with Brand. Do have a fix for the Shaco bug. If you have any information about Brand killing Kog'Maw in this way, please give any information you have.