Not sure whether they classify as obscure, but I haven't see cited already: - Dominator tree (https://en.wikipedia.org/wiki/Dominator_(graph_theory) https://en

Not sure whether they classify as obscure, but I haven't see cited already: - Dominator tree (https://en.wikipedia.org/wiki/Dominator_(graph_theory) https://en.wikipedia.org/wiki/Dominator_(graph_theory)) - Single-Connected-Components-Graph - Deterministic data structures (eg. a set that acts deterministic to the fact that addresses might be somehow randomly assigned, very useful for ensuring reproducibility) Already cited, but it's clearly among the most elegant: - union-find (!!!!) and as a bonus one that is easily overlooked: -std::deque, that when restricted to push_back() or push_front() guarantees not to ever move objects around.