I maintain list of ETF I use for my personal trading. I do mostly swing and position trades with them. I do not see liquidity as main issue as they are stocks tracking some basket or index.
If you want to daytrade them, then prefer some index etf funds like SPY, QQQ, IWM and so on. I would go to search ishares etfs as they are most popular etfs I think.
My personal ETF List