What is a good apology gift?

It is important to realize that a good apology gift is not something that will simply "buy" a person's forgiveness (since this rarely works) but something that will convey the sincerity of the apology more than Words alone and get the other person to consider opening up communication if they aren't speaking to you. Flowers are cliche and jewelry could be offensive. The best way to do this is to put a sincere apology in some form of writing that will get the person's attention and show them the extra effort you were willing to put in to do so. This is much more effective than simply apologizing with Words (especially if you have already done so before in the past), and is sure to open up lines of communication if the person isn't speaking with you.