Guar tastes too 'beany' for me. I'm been working on gravy a few months now. I'm not a big fan of xanthan as I find it gives gravies a slippery mouthfeel. I tried combining xanthan with other thickeners, using less and less each time until finally I came to the conclusion - I don't like xanthan in gravy. I love it as a stabiliser in cheese sauce to prevent curdling, but I'm not a fan of it in gravy.

Once you depart the soluble fiber gum realm, the options aren't overwhelming for potential thickeners. Vital wheat gluten goes stringy, soy flour doesn't taste that great and almond flour lends gravies a strange texture/taste as well.

So I turned to arrowroot - but only in moderation. The nice thing about arrowroot is that although it's slightly more carbs than flour, it has twice the thickening power. 1 T. (7 carbs) will thicken a cup of liquid. Since 7 carbs is a bit high for me, I combine it with some powdered gelatin and a little cream (for opacity) and get the net carbs down to 5. 2.5 net carbs per 1/2 C. serving works for me. It isn't zero carb like the gum thickeners, but it isn't slimy either.