It really depends on the functionality you are trying to get. Big names include SAGE CRM, Microsoft Dynamic CRM, SalesForce (which also started the whole cloud based CRM trend).
You can also find open source CRMs such as ZohoCRM and SugarCRM. It’s not an easy answer. You should search for what tools they will give you and do a bit research for the costs. Just a tip: Don’t assume that Open Source and Free CRM means zero cost. You have server costs, implementation costs and development costs (optional) that you need to consider.