Sterling VolTrader (formerly LVX) through Lime (formerly Lightspeed) Brokerage. It meets my simple needs for selling one-leg transactions.
Also recommend Multi Charts, MedVed Trader, Tastyworks, and Questrade.
Multicharts has a 30-day trial, same people that made
tradingview.com
MedVed Trader connects to lots of brokerages for data and trading. Superior charting. Customizable paint bars/scans/alerts. Visual trading from charts or DOM. etc.
Questrade for conditional orders for options. However, it is pretty boring.