GDPR is the EU's General Data Protection Regulation which comes into force on 25th May 2018
Here is an interesting article that explains what it is, and the impact it should have on companies' use of personal data.
https://www.cennydd.com/writing/a-techies-rough-guide-to-gdpr
The question this brings to my mind, is: Which companies are going to find their business models adversely affected? These might include data brokers, digital advertising services, social media, etc.
In terms of share price activity I don't see it having any effect at all. This is a relatively minor regulation compared to all the other financial regulations that companies adhere too. It's implementation is relatively straight forward too.
Maybe one or two companies will hype it up to generate incremental revenues such as https://www.investegate.co.uk/d4t4-solutions-plc--d4t4-/rns/celebrus-delivers-self-service-solution-for-gdpr/201802070900021116E/ but overall I see it as a non-event for any share holder.