How about a guild leaderboard for certain collective guild achievements? It would be a collective effort on the part of the guild to place in one of the topics (posted below). There would be no prize for placing in the leaders, just bragging rights. The boards would be reset every week.

Format for idea list: Name of achievement (description) - method of calculating score (example)
Here are my ideas:

Snarbolax Snuffers (# of Snarbolax defeats) - sum of # of times each guild member beats Snarby (party of 4 guild members = +4 to score)
Jelly Juicers (# of JK defeats) - sum of # of times each guild member beats JK (party of 4 guild members = +4 to score)
Roarmulus Ruiners (# of Roarmulus Twins defeats) - sum of # of times each guild member beats Roarmulus (party of 4 guild members = +4 to score)
Vanaduke Vanquishers (# of Vana defeats) - sum of # of times each guild member beats Vana (party of 4 guild members = +4 to score)
Boss Basher (# of total boss defeats) - sum of # of times each guild member beats a boss (party of 4 guild members = +4 to score)

Beast Butchers (# of beast class monsters killed) - sum of # of beasts killed, tier dependent, bosses count (t1 wolver = +1, t2 wolver = +2, t3 wolver = +3, Snarbolax = +5)
Slime Slayers (# of slime class monsters killed) - sum of # of slimes killed, tier dependent, bosses count (t1 cube = +1, t2 cube = +2, t3 cube = +3, JK = +5)
Gremlin Gladiators (# of gremlin class monsters killed) - sum of # of gremlins killed, tier dependent(t1 mender = +1, t2 mender = +2, t3 mender = +3)
Fiend Finishers (# of fiend class monsters killed) - sum of # of fiends killed, tier dependent (t1 yesman = +1, t2 yesman = +2, t3 yesman = +3)
Undead Usurpers (# of undead class monsters killed) - sum of # of undeads killed, tier dependent, bosses count (t1 slag = +1, t2 slag = +2, t3 slag = +3, Vana = +5)
Construct Crushers (# of construct class monsters killed) - sum of # of constructs killed, tier dependent, bosses count (t1 lumber = +1, t2 lumber = +2, t3 lumber = +3, Roarmulus = +5)
Enemy Eliminator (# of total enemies killed) - sum of # of enemies killed, tier dependent, bosses count (t1 = +1, t2 = +2, t3 = +3, boss = +5)

Crown Collectors (# of crowns made) - sum of # of crowns made from PvP/PvE, not affected by # of crowns spent or previous amount of crowns (make 1k crowns in a run = +1000 to score)
Serious Spenders (# of crowns spent) - sum of # of crowns spent on anything, not affected by # of crowns made (spend 1k crowns on a recipe = +1000 points to score)

Amazing Alchemists (# of item alchemized) - sum of # of items alchemized, continuations of lines count, not affected by star # (Calibur = +1, Valiance = +1)
Level Leapers (# of levels completed) - sum of # of times each guild member goes down an elevator, clockwork terminals/subtowns do not count, joining party mid-level does not count, a level must be played completely before the points of that level towards this achievement count (party of 4 guild members = +4 to score)

Lockdown Leaders (# of FFA/Team LD wins) - average # of LD wins amongst guild members, only guild members that play LD during the judging period are counted in average, guild must have at least 5 knights participating to be eligible (win = +1)
Guild Grapplers (# of GvG LD wins) - sum of # of wins for each guild (win = +1)

I probably have other ideas hidden in my mind, I'll edit if i get any more of them.