Before you jump to the conclusion that you were somehow overlooked on purpose, check to be certain that the mistake is not the fault of your firm's human-resources department or payroll division. If you were the only one left out of this bonus, it's possible that a simple mistake was made and nothing sinister was intended. If you find this to be the case, make sure to immediately tell your colleagues to prevent bad feelings from developing about your boss. You don't want to create a problem where none exists.
If your boss did decide to exclude you from this bonus, there isn't much you can do about it legally. In some European countries, however, if a company has paid a bonus for three years in a row, it may be required to pay one in subsequent years. You'll have to check with your lawyer or union if that's the case.
Assuming no mistake was made by HR or payroll, then it was clearly your boss's choice to exclude you from this bonus. Whether he or she acted cowardly or unfairly isn't the issue to focus on. You won't resolve anything or be able to change the situation with your outrage. For the sake of your future working relationship, you'll need to find out why you were excluded and what you can do to make sure this doesn't happen again. Show your courage by asking to speak with your boss. Remain calm and agreeable during this conversation or you won't get the results you want. Ask for tangible facts and examples of what you should have achieved -- with quantifiable results -- during the past year. Take copious notes during this conversation to show that you're interested in improving. The more you can remain silent and listen, the more impressive and powerful you'll seem. No matter what happens during this meeting, don't become defensive or you'll weaken your position. If the conversation helps to clarify things, then consider asking your boss to rethink giving you the bonus gift so that the office or department doesn't mobilize around this issue and develop morale problems.
If you sense that your boss doesn't care to improve the situation, it will only be a matter of time before matters worsen. So take the initiative to ask for a transfer to another department within the company, if possible. If not, begin looking for another job immediately.