Google isn't allowed to use the name 'gmail' in germany because someone owned the trademark 'g-mail ... und die post geht richtig ab' (or something similar). So

Google isn't allowed to use the name 'gmail' in germany because someone owned the trademark 'g-mail ... und die post geht richtig ab' (or something similar). So the big guy doesnt always win and an exclamation mark doesnt make a difference. So if you feel like it, go for it. You might win. (I don't know if the word go is to common to count as a trademark, though).