With the release of v2.0, this answer is now out of date. RTOFS, HRRR, and RAP are now supported and you can download the data directly from the LuckGrib server. There are many additional models that are now directly downloadable, which go far beyond the list above.
There are a large number of GRIB weather models. LuckGrib supports three: GFS; CMC and WW3. Each of these is a global model, with access made available through the NCEP/NOAA public servers.
GFS is perhaps the reference model used world wide. This is not to say that it is the best in all circumstances, but it has been around for a long time and many other models are compared to it.
GFS is a global model of the atmosphere. If you are interested in studying anything related to water, it does not help. WW3 is a model focused on ocean waves, but does not include any data on currents.
There are many models which focus on smaller regions, and offer some benefit beyond what CMC or GFS offer in those narrow regions. Often the regional or meso-scale models offer higher resolution; forecast data at finer time resolution; or some special knowledge of the area that is incorporated into the model.
There are future plans to support direct downloads of additional weather models. However, in the mean time, if you can get access to a weather model you like, LuckGrib is likely to be able to import it.
There are a number of relatively new weather models based on WRF, for example the HRRR or RAP. These models are not currently supported by LuckGrib, as the grid that the data is defined on is not in the standard format. This will be addredded in a future update.
LuckGrib is able to import ASCAT data from a variety of sources, OSCAR current data, RTOFS, and a wide range of other models.
If you have additional sources of GRIB data, try importing it into LuckGrib. If it does not work, if you could forward an example of the data to this site along with a short explanation on where you obtained it, we will try to support it in the future.
If you have a weather model that you would really like to download directly from LuckGrib, please see the question related to wanting a new feature in LuckGrib - mail the author and let him know.