Here's a start:
- Methuselahs are not notable unless they last at least half as long as the longest lasting methuselah that has the same [number of cells, bounding box, etc.] and are not trivial spaceship collisions from far away.
- Still lives are not notable unless they form naturally or can act as catalysts/eaters in a way that no smaller one can.
- P2 oscillators are also not notable unless they form naturally or can act as catalysts/eaters in a way that no smaller one can (ASIDE: but I've only ever seen three p2s that can act as a catalyst in a non-trivial fashion: blinker, toad, and the griddle variant in the p22 TL hassler).
- P3-6 and 8 oscillators are notable if they have an interesting property (natural, sparks, etc.) or are a reduction of something already known; other such oscillators should be relegated to the Useless Discoveries thread.
- P7 and P9+ oscillators are generally notable, unless they are composed of two lower-period rotors.
- P2 and P3 spaceships are not notable unless they have sparks or are edge-repair ships.
- P4 c/2 spaceships are not notable.
- Other P4 and P5 spaceships are not notable unless they are small, have sparks, or are edge-repair ships.
- P6+ spaceships are generally notable.
- Conduits are notable only if they turn one reasonably common active object into either another reasonably common active object, a reasonably uncommon stable object, or any spaceship; and they are not a trivial modification to something already known (except catalyst reductions).
- Syntheses are notable only if they are for a reasonably uncommon object and they either cost at most two gliders more than the current best or they have some remarkable property like being slow, edgy, one-sided, etc.
- No pattern deserves its own topic unless there is no topic available where the pattern could be posted or it is a major discovery that has been awaited for some time.