The 5 suspect players are lined up.
Their classes are: Soldier, Scout, Heavy, Engie and Medic.
Their hats are: Gibus, Bill's Hat, Pillar of Hats, Proof of Purchase and Professor Speks.
Their favorite maps are: Dustbowl, Nucleus, Harvest, Badlands and Upward.
And their melees are: Necro Smasher, Pan, Ham Shank, Consciencious Objector and the Saxxy.

The Clues: 
1.   The player with the Gibus stands directly next to the the player holding the Conscientious Objector. 
2.   The Heavy likes Badlands. 
3.   The Medic stands to the right of the player wearing the Pillar of Hats. 
4.   The Harvest fan stands directly next to the player holding the Pan. 
5.   The player wearing the Proof of Purchase stands directly to the left of the player who likes Badlands. 
6.   There are two players between the Professor Speks wearer and the Dustbowl fan on the left 
7.   The Engie wears the pillar of hats. 
8.   The person with the Necro Smasher stands on the far left.  

9.   There are two players between the Medic and the Proof of Purchase wearer.  

10. There is one player between the Heavy and the Nucleus fan on the left.  

11. There are two players between the Gibus wearer and the person with the Pan.  

12. There is one player between the Professor Speks wearer and the person with the Ham Shank on the left.  

13. The Soldier stands directly next to the player with the Necro Smasher.