I use RSK on Money-on-Chain, basically holding some of my rBTC as BPRO, which gets a small leverage (and also earn fees from the protocol while at it) on the price of BTC in exchange for being the collateral for the Dollar on Chain (DoC).

Also on Sovryn to play around a little, and learn about the zero lines of credit (borrowing zUSD at 0% interest using rBTC as collateral).

I haven't had the need to use DoC or zUSD yet, but I played around with something like 5 DoC once.