SQL's most egregious reserved keyword is, in my opinion, "user". Almost every application will have a users table. I gravitate towards singular table names these days [1], and SQL sitting its fat behind on the word "user" means I always have to defer to "users" just for the users table. There is almost no other keyword that I regularly run into conflict with other than "user". I don't even use the "user" keyword in any SQL queries, what a terrible trade off.
[1] I used to prefer plural names, but now I favor singular names because no naming headaches with the plural intricacies of the English language.
[1] I used to prefer plural names, but now I favor singular names because no naming headaches with the plural intricacies of the English language.