Great question and see it all the time. I agree with Jay and Stephen. K.I.S.S.
One thing you might also want to define will be how easily accessible is the information for the actual sales team. Meaning do you want it native to your CRM or do you want them having multiple windows open.
Also, it will depend on who your ICP (Ideal Customer Profile) is and what role they have? Are you selling to IT, Sales/Marketing, or something else.
Research Tools: LinkedIn, InsideView, TwitterContact Information Tools (Email/Phone): SalesLoft Prospector, InsideView, Discover.orgCommunications Tools Email: SalesLoft (Cadence), ToutApp or Yesware, Velocify, and ContactMonkeyDialing: InsideSales.com, Connect & Sell
As you can see this actually turns into "What's in Your SalesStack" as opposed to one-offs. You are welcome to contact me offline if you have other questions.