Good Ol’ Onyxia
You have a level 90? Why don’t you do some of the old raids?
Nowadays, you don’t need to be in a raid group to enter any pre-pandaria raid. No more bothering your friends with: “Can anyone plz go into a raid group with me, so I can enter xxx?” And no more losing friends when they find out they don’t get their quest done because they now are in a raid group.
Besides, many of these raids have interesting drops.
It is the case of good ol’ Onyxia.
I soloed her with my level 80 back then, when she was a level 60 mob (but it wasn’t very easy). Then Blizzard upgraded her to a level 80 and revamped the loot.
That means that she has the very incredible mount called: Reins of the Onyxian Drake. A beautiful mount enjoyable by all your characters nowadays. The only problem is the low drop rate.
Besides that, she drops many epics: a quest starting item and a bag that contains epic gems. Some of them are still selling pretty okay on most servers (especially if you have a jewelcrafter who can cut them, as they still are among the best gems, you can put into lvl 70 gear).
Even more, the epic you get can be disenchanted into Abyss Crystal, which still sell pretty okay on most realms.
The whole run takes no more than 3 minutes if you are decent geared. A bit longer if you are not. So no reason not to do this raid once a week, right? (Scorpyo)