[Shaun]

Bekki was the show's first ever victim of a baying mob, she was hardly irrelevant. I remember the backlash against her Judas kiss being massive.

David, Pav and Gos certainly contributed to their series as well, however crap they were.

And if you're going to include two BB11 housemates then how about Keeley, JJ or Jo ahead of Steve?

For each series, I'd say the most dispensable were:
BB1 - Andrew
BB2 - Elizabeth
BB3 - Sunita
BB4 - Steph / Nush
BB5 - n/a really
BB6 - n/a really (although I could've quite happily done without Orla)
BB7 - Jonathan / Michael
BB8 - Liam / Amy
BB9 - Nicole tbh (what a waste of time?)
BB10 - Cairon / Tom
BB11 - Keeley / Laura
BB12 - lol take your pick (i'd say Maisy)
BB13 - Victoria by default I guess, only stand-out moment was her evil eyes
BB14 - Sophie
BB15 - Winston / Kim / Zoe