I'd second CND Brisa, which is a hard (file-off) gel. I've also used Calgel for many years, which is a soft (soak-off) gel. The primary reasons (and there are many) that I prefer Brisa over other gels, are that it is a much higher quality gel, it doesn't yellow with age or sun exposure, it has beautiful clarity, it contains higher-quality photo initiators (meaning there are fewer of them, so the client doesn't experience the dreaded 'heat-spike' you will hear mentioned), it is hypoallergenic (a rare find in a gel), it is not runny (so it stays where you put it and has fantastic workability).. I could go on!