John Kerry says one thing then allegedly changed his position and he was a flip flopper. John McCain does the something similar but worse and he's a Maverick. Ergo Maverick=Flip flopper.
1. Bush Tax Cuts
2. Religious Intolerance
3. Campaign Finance (a bill which has his name: McCain-Feingold)
4. Immigration (a bill which has his name: McCain-Something else)
5. Torture
I'm sure there are more but those are the only ones that occur to me right now.