When it comes to cybersquatting laws and trademarks you really need to be VERY precise with what you say. You started this thread with no details .. as such .. ALL subsequent answers are just guesses (including my own)
There is a HUGE difference between "
First+Last Name" and just "
First Name" (alone) or "
Last Name" (alone).
That being said .. there are still plenty of grey zones even with one words/names. NEVER EVER take advice on what to do with a specific domain from someone who does not know the exact domain AND know the circumstances and specifics of the potential conflicting name/brand.
A big factor is uniqueness .. because at the end of the day it's a judge or UDRP panellist who is going to judge whether or not you registered the domain in bad faith or not.
Also remember that a name/mark does not need to necessarily be considered a trademark .. PARTICULARLY when it comes to names. The moment someone uses a "mark" in commerce, it is effectively a trademark even if unregistered. So if you use your name for business purposes, even something as simply as putting in in your email signature can potentially qualify that as being your "trademark" (within the specific class and territory) .. just as it could potentially put you in conflict with someone's trademark.
To further complicate things .. business can most certainly use single names (first or last) as trademarks .. even if it's just a random name.
My advice .. 100% DO NOT register any potentially conflicting domains until you have learned much more on trademarks, UDRPs and how both relate to domains. There's TONS of information on the subjects all over NamePros!