That is a hard question to answer without knowing more about your needs and goals.
If you are seeking a very simple, yet robust NTRIP Client for use on a PC, one of the best choices would be the free product offered by Lefebure Design, LLC see the site at:
This is the tool of choice, hands down, if you just want a very simple and direct way to get corrections onto your desktop and out to a serial port into your GNSS. No GNSS tools to clutter things up, just a bare metal connection. He also makes an Android variation that uses Bluetooth to send the stream to your GNSS.
No discussion of NTRIP Clients would be complete without mentioning the work of the German GDC (GNSS Data Center) in creating the BKG Ntrip Client (called BNC) which is maintained by Leos Mervart and Georg Weber, among others. You can download this tool, both in compiled and in source form from: http://igs.bkg.bund.de/ntrip/download
At the bottom of the above page you will also find a listing of many of the key NTRIP Clients and other related tools used by both professional and amateur practitioners in the art of RTK navigation.
Many GNSS vendors provide an NTRIP Client for their own devices. Often these clients are available at no cost. By contrast, NTRIP Servers and NTRIP Casters tend to cost quite a bit, which makes SNIP an effective solution in such cases.
Build one yourself….
For Programmers: It is fairly easy to build an NTRIP client if you have any experience with TCP/IP. but it can be a bit challenging the very first time. Some of the links above, as well as some of the open source projects like RTKLIB, can get your first programs going. In essence, your code will connect to the Caster (picking which stream), and then pipe that stream over a serial port to your rover GNSS device. You never need to understand or decode RTCM, but of course that skill can be of value. You can also use SNIP‘s build-in RTCM 3 decoder & viewer and its universal decoder functions to help you with you development, another unique feature present in SNIP.
See also this related article for more NTRIP Client choices.