The Achievement TAKE OFF, HOSER requires you to ride CHOMPY (the cleaning robot) for a total of 5 minutes in a single game! Below is a video and written walkthrough depending on your learning preference. Enjoy!
For Maximum points, follow the guide below.
Round 1: shoot 4 times, then knife
Round 2: shoot 7 times, then knife
Round 3: shoot 9 times, then knife
At the start of the game, shoot the zombies 4 times, then knife. Once you have 1,450 points, open the door to the ARMORY and then activate the power generator to your left/right (depending on if you started in the hangar/gun deck). You now have 300 points.
Toss ALL of your grenades into the grenade disposal (giant plinko board in the ARMORY). Depending on the amount of points you get, you should be able to buy contact grenades off the wall. The first time you do this, you will receive FOUR more grenades.
Toss ALL grenades again into the grenade disposal. Finish off the final zombie by shooting 4 times and then knife.
At the start of round TWO, you will receive another grenade, so toss that in the grenade disposal! Shoot the zombies 7 times, then knife. When you have enough points, open the door to the LIFT and stand by the CARGO door.
At the start of round THREE, continue to shoot 9 times, then knife! You should have enough points to open the CARGO doors. Activate the power to your right, grab the Exo-Suit, and punch zombies until you have roughly 1,000 points.
Activate DOOR #34 for 500 points. CHOMPY will enter the door. Climb on top and ride him around, until he goes back into Door #34. Wait until it cools down, so that you can activate it again. If you need more points, remember to use the grenade disposal machine!
AVOID KILLING ZOMBIES AS MUCH AS POSSIBLE. Why?
Chompy will kill quite a few zombies and trigger more rounds, so use the grenade disposal machine to up your points, shoot zombies with your pistol and then punch them for the killing blow. You should receive this achievement way before ROUND 10!