In the middle of being strangled at Soo Lin’s flat, Sherlock tries several times to gasp out “John.” It’s either a warning or a call for help, either of which are heartwarming. And then, afterwards, Sherlock refuses to tell John what happened and that he nearly freaking died. Extra heartwarming when you remember the conversation Sherlock and John had in A Study in Pink about what a person would say if they were dying, if they’d been murdered. In what he may have thought were his “very last few seconds”, Sherlock didn’t say anything remotely clever or imaginative. He simply said “John.