Set the scene, marines inside landspeeder, tyranid horde ambushes them and attempts to attack them, the Marines, in their best interests , decide to GTFO the moment it is the Pilot's turn … 
However… Storm Warden Devy decides upon himself to jump out of the speeder, Brace his weapon, and start shooting at the biggest thing he sees (a near hopeless action as he is heavily out numbered…
The rest decide  to leave the poor bugger to his fate for his stupidity…. however the Pilot, being a space wolf and a bit of a dare devil, proposes to me that he will tilt the land speeder so the side lower to the ground is the now empty seat of the devy, and try and scoop him up whilst moving… a ballsy move, I tell him that it should be a -10 (I felt generous) Pilot's test…. he needed 35 … he got 36…..
Me feeling like a sympatheitc little twurp decided that, due to the chaos of the incoming fire, the land speeder actually jolted, swirved ect ect, so… rather than the "door" side facing this, at the time unsuspecting, devy… It was instead the speeder's hood and, as you probably have guessed, he went straight into the bugger…
Pinned to the front of the speeder, the pilot decided there was no time to correct the mistake so, for the next few  kilometeres of the journey, this poor marine was stuck on the front of the speeder, his battle-brothers all but giving in to the humour of the situation through a distinct feeling of anger towards the dev's pure idocy…. 

Well he was not on one of the guns and… well…. I am GM , what my players do in the heat of the moment is nothing to do with me…  xD 
He decided upon himself to jump out and meet the enemy head on! Can't knock him for that! xD