#1 Zinedine Zidane
Zinedine Zidane has been linked with the Man United job ever since he parted ways with Madrid, back in the summer. He's by far the most likely candidate to take over the role permanently, given his success and the fact he's currently unemployed.
Now that Mourinho has been dismissed, Zidane will undoubtedly be near the top of United's shortlist, and without any clear obstacles in his way, Zidane's appointment could be announced very soon.
At the time of writing this, Sky Bet have given Zidane 5/1 odds of becoming the next United manager.
However, the one thing that might mean other managers step ahead of him in the running for the job, is the fact that his first-team managerial experience is restricted solely to his time with Madrid. He spent two years there, and whilst he did achieve great things, some might argue that it was down to the calibre of players out on the pitch that did a lot of the work for him.
Rumour probability: 9/10
As stated above, Zidane is the most likely candidate for the job, but it might be his experience that lets him down slightly. Laurent Blanc and Mauricio Pochettino (if he's willing to leave Spurs) will be difficult competitors to surpass, but only time will tell what happens from here.