Actually, if it is gambling sites in which Bitcoin is being used as the mode of payment with every deposits and withdrawals, there will be too many to mention. At this moment, most of the gambling sites are block chain based or simply have adapted crypto system as replacement for fiat digital currency which were used before in online gambling. People nowadays do prefer cryptos over fiat especially in online activities because they do think that the transaction fees cost less and also, faster in such way. No wonder why other online services are doing the same thing which is adapting the use of cryptos. I am currently playing in an online casino wherein Bitcoin is their mode of payment. Many gambling sites are open for variety of cryptos, which is an advantage for them, as they were saying.
But personally, I do prefer a single crypto currency with regards to the mode of payment in online activity such as online gambling. Security is already there as well as convenience.  But going back, most of the gambling sites are blockchain based, that's the main point. As I've said some gambling sites are accepting multiple cryptos and some are into only one. It will just depend to the players on what they prefer the most. Sports betting sites are also on the rise nowadays, which is somewhat popular to many gamblers in this industry.