My advice for people coming up with taglines or slogans for their company:
Don’t pay attention to billion dollar brands!
Example: Apple's slogan of: “Think Different”
Instead, you should pick a slogan based on your size:
• Small Company: Be very direct.
• Medium Company: Can be slightly vague.
• Big Company: Aspirational.
When you’re a giant brand you have many products and many services, so a “direct” slogan is hard.
That’s when you can go aspirational and vague like:
My personal opinion for best big company slogan is Geico, because their slogan also SELLS!
More resources on taglines and slogans: