A few decades, this would seem like a totally meaningless question. This is primarily because in the past everyone got married either according to the customs of the land or according to the religion that they are a part of. Now though, you will realize that this question is definitely relevant. To have a proper answer to such a question though, you need to recognize the choices that are present to you.
The first choice is the traditional religious representative. For those who are willing to continue using the traditional and or cultural customs to get married then you will effectively be answering the question to be someone who is either a priest, rabbi, Shinto priest, or any other religious representative that you are part of. For some it is the community leader who also doubles as the religious leader for the community that will perform the wedding ceremony for everyone in that area.
For those of you who would rather move away from a traditional wedding at a church, mosque, shrine or some other religious house you would more likely be having a civil wedding. This is a wedding recognized by the state and without any or very little religious connotations. The officiant is a person who is legally able to do the wedding ceremony. The person can be a male marriage celebrant or a female. As long as they are legally able to perform the ceremony they can be the officiant. This is one of the reasons that civil or modern weddings are becoming more popular. As there is no restriction to the sex of the person officiating the wedding ceremony people who want no religious customs in their weddings or a specific person to officiate over the ceremony tend to choose this option. As such they are provided or look for persons who provide such services. These persons are normally called civil celebrants.
Another choice some persons may use is having a friend do the wedding ceremony. The friend may not be legally able to do the ceremony but, that simply means that the couple needs to go the government civil agency to obtain the marriage documents. Some couples rather this option as it makes for a more personal ceremony which they wouldn’t get with a civil celebrant or a religious figure.
Now that you are aware of the choices available to you then you can decide who you want to use for your wedding. So would you rather go traditional and have the customary religious figure perform the ceremony? Or do you want to break from the norm and have a civil wedding officiated by a civil celebrant in wedding of your style and location choice? Maybe you want to keep it personal and have a close mutual friend perform the ceremony to give it the ceremony a sense of close family and friends. Whichever you choose make sure it is one that you will not regret and will make the ceremony one that is remembered by you and the others who attend.