屡见不鲜 should the last character be third tone rather than first? It's first tone in Baidu, zdic, Skritter and others, but it seems the "few / rare" third tone meaning would make more sense. I asked one Chinese speaker and they said it with third tone. Also this page http://www.tieku001.com/507301/16.html says the first tone is a common error (item 234 in a list of common errors). Opinion of Skritterers?

I checked a couple of Chinese dictionaries and it should be xian1 - one dictionary had a special note about the pronunciation. The chengyu describes something that is “多次見到，並不新鮮“. The English definition on skritter doesn't made the lack of 新鮮-ness clear.

There are a fair few pinyin errors in skritter, so it's worth being vigilant. But in this case it seems correct.

It is listed with first tone for all my eight dictionaries that contains it in pleco.

If one considers the modern meaning of 屡见不鲜, which is “something commonly seen and not rare”, then it is easy to jump to the conclusion that 鲜 should be third tone. But this is a 成语, and it has a story behind it. In that story, 鲜 refers to a freshly killed game, and so should be first tone.

More information can be found if one looks up 数见不鲜, which is a variant of 屡见不鲜. From zdic, under the tab 成语解释, the explanation for 鲜 is "鲜：新杀的禽兽，引伸为新鲜。本指对于常来之客，就不宰杀禽兽招待。后指常常见到，并不新奇。" The TW MOE dictionary also gives a similar explanation for 數見不鮮 and reaffirms that 数见不鲜 and 屡见不鲜 are just variants.

Interesting. FWIW, 現代漢語規範詞典 in the entry for 屢見不鮮 also says「注意 “鮮”這裡不讀xiǎn, 意義跟“少”不同。」