I chose Silicon Graphics (08:00:69) and it's fascinating to see that anyone else did, for any reason. For reference, my ISP hands out 2-8 IPv4 addresses, expiry indefinite (unless I power down), to clients connected to the cable modem. So my stack looks like

[Motorola Surfboard]->[4p 1GbE Switch]->[Linksys E3000 (08:00:69::)]

Depending on the mood of the ISP, I can have several other networks running from the 4-port switch. If I spoof those MACs repeatedly, I can get an arbitrary (within range) block of public IPs, and there's some seriously weird behavior in allocating those IPs (change my MAC 48 times in a row, end up on the same IP I had just lost from a power outage?)

I always use Sage (the accounting software folks) one of 00-80-2c as it's burned into my memory 30 years later after working on Sage Mainlan back in the days...

Looking at the list I'd go for SpaceX (00-26-12)