I use TD Ameritrade's thinkOrSwim platform to do all of my analysis, charts, store watch lists, etc. It has a fairly high learning curve but truly has everything you could possibly want.
However, for performing the actual trade I'll just go into whatever account the money is in. I have several (different 401ks, taxable, Roth, etc) but like Fidelity for having the lowest trading fees although their interface can be clunky. But like I said all I'm doing is putting the order in after doing analysis elsewhere.