I really like the DMR and consider it to be the best weapon out of the Halo series due to it's high accuracy, range (when used correctly) as well as being a weapon that is not overly overpowered, it has that sweet spot in the middle that fans can adore much like to it's predecessor, the BR from Halo 2-3.
But of course the DMR has a stronger advantage to the BR due to it's firing capabilities such as being almost effective at firing at most angles, whereas the BR has a shorter firing range which makes it more challenging for players to use the BR against enemies in combat, so basically the DMR is the best weapon at covering all battles taking place at many different angles.
Although it takes up to atleast 5 shots for a DMR, I still consider it to be the best weapon in the game due to one or more several factors such as it being beneficial for long range combat as well because of it's scope attachment, heck most long range fights with the DMR you could get the clear shot with the scope unzoomed, just as long as you keep your firearm crosshairs on the enemy player.
Another reason yet again as to why the DMR is the best weapon is primarily due to it's smooth deliverance of headshots because the weapon contains far less recoil power compared to the BR; which of course helps players reap the benefits of scoring more points.
A weapon of that caliber is somewhat handy in getting the best headshots in a online match or peppering Elites in Firefight mode.
Of course though if you are abit of a noob like me then obviously it requires alot of practice into getting kills. Did I mention it can deliver a huge impact on creating a great advantage for you and your teammates on many Halo maps in Assault, Slayer, SWAT and other large mapped matchmaking matches?