>>749
>>What is べ at the end of a sentence?
Usually imperative:
喜べ
yorokob-e
Rejoice!
But that's "-e", not necessarily "-be":
動け
ugok-e
Move!
"-be" is also a stereotypical suffix of provincialism, sometimes used by young urban people to make themselves sound funny. You can attach it to any indicative predicate:
行くべ
ik-u-be
見るべ
mir-u-be
悲しいべ
kanasi-i-be
>>Also, when it comes to speaking to your girlfriend/wife, is it considered rude to use やる-form? As in, 買い物を買ってやる。?
Not necessarily. But it is less affectionate than あげる.
>>Also what about 「俺」？ I know that might be somewhat rude to just a girl, but if it's your girlfriend I imagine it might be different.
The rudeness of 俺 is determined by the seniority+status, not the gender, of the person you are speaking to. You can use it to a girl whether or not she is your girlfriend.
>>Then again, I've seen people use polite speech with 「俺」..
Yes. You can combine it with the polite "-se/-desu" style:
俺が やります
ore-ga yarimasu
俺に ください
ore-ni kudasai
But using it in a formal public statement is definitely not a good idea.