Seagate (yep really!), they're enterprise grade drives that have spent five years sitting in some under-loaded corporate server (nobody chooses 3.5" SAS for heavy loads) and now have an even more restful life in my NAS[1]. They were also very cheap - I'm a great believer that the I in RAID should not be an E. I'll also take second hand enterprise gear over fancy domestic gear any day.
[1] Yes that is also second hand enterprise gear - it's a supermicro rack tuned down to be just fast enough to saturate both LAN interfaces serving NFS from ZFS and decrypting the drives.