So, I've been looking for this since DZ first came out, now that I finally found a way to do it, I decided to tell you guys how to.
1. Create game_player_equip entity
Press the Entity Creation Tool and in the Entities category, choose the object game_player_equip and place it wherever you want in your map.
2. Game_player_equip edit
Press game_player_equip entity twice to go to it's properties. In Class Info press SmartEdit and then add a New Keyvalue by simply pressing the Add button in the right. Name the key weapon_fists and set the value to 1.
3. Create logic_auto entity
Press the Entity Creation Tool and in the Entities category, choose the object logic_auto and place it wherever you want in your map.
4. Logic_auto edit
Press logic_auto entitytwice to go to it's properties. Go to Outputs and add a new Output by pressing Add... in the bottom of the window. Now in My output named select OnMultiNewRound, next in Targets entities named write weapon_fists, in Via this input select AddOuput and finally in With a parameter override of write classname weapon_knifegg
And that's it, as you can see, it's very easy to do. Hope I helped you guys!