The stingray x clone by sxk is really good. My button was crunchy at first but when I took it apart it was full of machining oil. Cleaned that out and smooth as butter.
I've got the SXK Stingray X as well, LOVE it. I also have a fastech Nemesis clone which isn't TOO bad, however it will be better when the switch magnets arrive and then it will be hard to decide a favourite between the two. If you're undecided about what clone you want to buy, I'd suggest looking at Inifinite clones, I have a few of theirs (rda's though) and all of them have great quality compared to others like Tobeco - I wouldn't hesitate to spend money on one of their mods as well.