Yeah I'm a weirdo I have this running order game I play.
1.Engineer
2.Heavy
3.Medic
4.Pyro
5.Soldier
6.Scout
7.Sniper
8.Spy
9.Demoman
If there's already one of them on the team I go to the next one and the next one and so on. I have to stay with that class until someone else on my team picks the same one in which case I start at the top of the list again. The only exception being when playing defending engineer on attack/defense in which case several engineers makes sense.
1.Engineer
2.Heavy
3.Medic
4.Pyro
5.Soldier
6.Scout
7.Sniper
8.Spy
9.Demoman
If there's already one of them on the team I go to the next one and the next one and so on. I have to stay with that class until someone else on my team picks the same one in which case I start at the top of the list again. The only exception being when playing defending engineer on attack/defense in which case several engineers makes sense.