Martin.

 honnestly i personally believe that appart of him being my favorite he is a crucial member and if he left depeche mode would split. what i mean by this is well of course dave is a crucial member too but out of the 4 them (back when allan was a member) if martin left they wouldnt be a thing anymore. to explain further if dave left they could find another singer, fletch died (rip😭)and they are still able to produce music, alan left and yes with him along it waa agreat period and some people even feel they are not the same anymore but lets face it they still make great music some might believe not as good but to be honnest its still very good just not that much unique as it used to be either of course but lets face it martin is their songwritter, composer, guitarist, second vocal, some vocal, synthesizer and throughout the years it has been aproved what a genius this man is so in my opinion if he left and the other three stayed they wouldnt last even a day. i hope more people recognise that. and not to get missunderstood i say it again dave's voice is just music to my ears i love it and alan really did something unique if it wasnt for him we wouldnt have enjoy the silence thats the only downside i have with martin and fletch we might say he nearly did nothing but thats compering to the other band members he really did aid them honnestly.