Some of the more public events I've enjoyed were the MHC Hunts, back in the early days of the guild (and even before it became a guild).
Essentially, anyone who wanted to come, was welcome, and we met at the Luna gate at Midnight (hence Midnight Hunters Club), and went to remote places to hunt, to get people into areas that few rarely ever ventured (favorites were Blood Dungeon, and the areas between Compassion & Chaos in Ilshenar, such as the desert, the dungeon (Rock dungeon?) and the area between that dungeon & Chaos).
Another activity we did were public Treasure Hunts. We'd take 1 level 6 map per person, and that one person got to loot the chest, while everyone else killed the spawn.
Lastly, There was once an Alliance PvP Scavenger hunt - in a non-PvP guild. It worked as follows:
1. All participants used only normal leather, non-exceptional, armor, dyed a specific color to make the participants recognizable. Weapons were normal material, exceptional quality (since there are damage limiters for PvP that don't apply to PvM).
2. members of the one alliance guild that was put together to attempt to sneak into Fel and do a champ or two when the big guys were killing each other elsewhere, were scattered in all the Trammel cities, and were similarly equipped.
3. The hunters had to go to those cities, challenge the character there to solo combat, and fight them. The first three hunters to win at any given city would be given a locked chest with some mid-range (at the time) loot, like low-end doom arties, minor Artifacts, checks, etc., by the other person, once rezzed, or by a referee that recalled in with the prize, after the challenge character reported a death.
4. Any template was allowed, but no pets were allowed, and combat had to be on foot.
5. There were three grand prizes, based on who brought the most chests back to the start point at the end of the event.
I finished in the top 3, using my BLACKSMITH. Sure, he has 120 Blacksmith, and 100 Mining - but he also has 125 STR, 60 DEX, 120 Macing, 90 tactics, and the rest of his points scattered in Parry, healing, Anatomy & Chivalry - and the generic weapon they provided for the macers was a Mace - which has DISARM as a special move.
I walk in, they look at my equipment, see all is in order, and my skill title for blacksmith. they are a bit amused - until I start chaining Disarms, and killed them each in about 10-15 seconds. The archer was a particularly fun kill. The really fun thing is that most of them had broadband, and I was still using dialup at the time.
As I left, I made the comment - "Remember, now and forever, that you got pwned by a legendary Blacksmith." (granted, one that actually has gone to the doom gauntlet before, and hunts Valorite elementals for fun, but they didn't need to know that until later)