My personal record is 113 species in a day in Lehigh County, PA. It would have been the county record, but a friend of mine got 117 the next day. He didn't intentionally try to beat me. Just a coincidence.
I don't know what the current PA state Big Day record is, but I know there was a record of 160 species in a day back in the '80s.
The record for the "World Series of Birding" in New Jersey is 232 species seen in the state in a single day.
Think my PB is about 107, ironically from my non-birding years when I made up the numbers in a birding race in Northumberland; the winning team as I recall had 120+. I remember also having a high day list from a visit to Bharatpur in the early 80s, also from my non-birding wilderness years.
I guess the Peru total quoted upthread is probably a world record, but I remember reading a while back about a team in Catalonia who posted a massive 'big day' list, a European record?
I managed 101 on a may bird race in Dorset as a teenager in the 1980s, and 170+ in Hong Kong in a year when the winning team made 180+. This year my team managed 145 species.
My current patch at San Tin is an area of fishponds, some tree-lined drainage channels and a small urban park right on the boundary and loomed over by high-rise Shenzen. My record is a tantalising 97 species but the record is 113!