I've had two Big Mek "characters" in my army. One came into being as part of the Nobs mob in 3rd. edition where he was just a lowly Mekboy toting around a Kustom Force Field that looked like a satellite dish, he was known as Duruk Rukus... later to be known as Duruk "Da Fixxa" Rukus when he became a Big Mek.
The other Big Mek character that led my Kult of Speed forces atop his kustom Battlewagon was Shuvva Luggitz who carried an old school Shokk Attack Gun that counted as a "Supa-Force Field Projekta" which in game terms was a Kustom Force Field and a vehicle Force Field from the Apocalypse: Kult of Speed army list. Shuvva led my Speed Kult to numerous victorys in 3rd and 4th edition.
Now that the Shokk Attack gun is back I can field both Big Meks if so inclined. Character wise, I was always partial to Shuvva Luggitz but I am more inclined to field Duruk 'Da Fixxa' Rukus and the newer Big Mek model with the Kustom Force Field. One day in the future I may actually convert a fitting Shuvva Luggtiz model as I always invisioned him with a Power Klaw but for right now I'm good with 'Da Fixxa'...