I really like original Conspiracy X's (not seen the new Eden edition, which uses their new system house system) psionics system, just the idea of using Zener cards as the random element and having to guess the card the GM is holding is cool. The more powerful a psionic your character was the more guesses you could take.

I heard one person once complain that it wasn't a fair system as the player needed to be psyhic to rather than the character..... erm right it's just novel randomizer, using cards instead of dice, you loon!

So what are your favourite, interesting, novel or just plain does what it needs to do mechanics and why?

Take 10 and take 20 (d20): The old bugbears about "trying again" and fumbling on simple tasks meet their end with this simple, effective thumbrule.

Fate's pyramids and aspectes:
- The pyramid is a simple yet open way of structured chargen, and even creates a traveller style mini-lifepath that equates background to abilities.
- Aspects are a useful compromise between keeping behaviors realistic and permiting player sovereignty over characters.

Speaking of which:
Traveller's lifepaths.

"Per incident" flaws (e.g, Backgrounds in Spycraft, flaws in nWoD, drawbacks in Vigilance/Haven d20/Modern drawbacks, other games like 7th sea features this as well) I have come to loathe traditional "point farm" disadventages that encourage players to seek whatever disads they think will get them the most points for the least impact, and is insensitive to campaign conditions. Providing points when it actually impacts the character seems to me to be the "way to go."

Hmmmm.

I like Palladium's phased combat system.  One person attacks, then the other person defends.  If that defense takes an action (is a dodge), then they lose their next attack and are forced on the defensive until next round or their can turn the tables on their attacker.

I like the dice trick in Silhouette and ICON, rolling a bunch of dice and taking the highest.  Silhouette has a better way of dealing with critical successes (if any other dice other than the highest roll 5s or 6s, they each add one point to the resolution total).  But ICON has the dice trick the right way around with Attributes determining number of dice to roll and skills being directly additive.

I used to really like the damage and staging numbers in Shadowrun 1e.  Basically, each weapon did a base damage, say Moderate.  A single success on the attack roll would indicate this base damage was inflicted.  But for every number of successes equal to the staging number of the damage (a number between 1 and 4), the damage category went up.  So, if I had a weapon that did Moderate base damage, and had a staging number of 2, then I could do Deadly damage if I rolled 5 successes on the hit roll (1 to hit, 2 to upgrade to Serious, and 2 to upgrade to Deadly).  At that time it was really novel to have the attack roll determine the base damage as well.

I tend to like rolling lots of dice.  It makes me feel like I'm doing something big when I have a handful of dice to roll for an action.  So, I enjoy playing dice pools.

When I design my own games, I usually go with the old tried and true attribute + skill + die roll against a difficulty or opposed roll.  For my starship game I use a die pool which functions almost exactly like the old Storyteller system.  Although it looks like I copied the mechanic, it was more of a parallel development sort of thing.

DJ's Difficulty Rating (DR). Depending on the difficulty of a task you get a multiplier from times four down to times one tenth. Meaning that if the base chance of doing a task is 30%, the adjusted can range between 120% (95%, but with an increased chance of getting a special result) and 3%.

The agriculture rules are fun too, and can provide tons of plot hooks.

As I said in another thread:

Dynamic Sorcery from BESM.

A complete magic system in one page is an idea that appealed to me so much that I just had to do a Fudge version of the same.

It so impressed me that I have a distinct distaste for huge spell lists in RPGs.

The chase rules from Spycraft (1st ed., haven't read 2nd ed.). Abstracting the fuck out of it to give a good narrative chase while rewarding player and character ability, awesome minigame.
-Zam

The magic system in Ars Magica (as well as the similar mechanics in Mage and Nobilis), for the sheer versatility of the available combinations.

Also, the inverted damage tracking in Nob, for its absence of cluttered record-keeping.

1. Blue Planet's initiative.
2. HeroQuest's character creation.
3. Deadlands' merits and flaws system.
4. Silhouette's wounds and vehicle systems.
5. Storyteller's core mechanic.
6. Blood!'s critical hit tables.

EDIT: Forgot the because.
1. It seemed to make the most sense of any.
2. Open, yet deep and very individual.
3. Encourages people to actually play them out.
4. Quick, easy, yet felt balanced.
5. I find handfuls of dice to be pleasingly tactile and the smaller numbers made it easier for new players to cope with, it also made NPCs a doddle (until you got into werewolf or exalted powers).
6. Gory and fun.

Plain old hit points.

Pendragon's Traits and Passions. They provide an interesting way to encourage roleplaying without really forcing anything.

Quote from: ColonelHardissonPendragon's Traits and Passions.

Seconded.  Also enjoy Traveller's char-gen, Unknown Armies' Madness Meter, Drama Points from Cinematic Unisystem, the freeform char-gen in Over The Edge, and the utter simplicity of combat in Tunnels & Trolls.

Pendragon – Traits and Passions are a great way of nudging people into genre. I'm also very fond of the whole Wounding/Healing/Death complex of rules.

Sorcerer – the combat system (also known as 'complex conflict system') is a brutal and efficient machine (try the John Woo stand-off test). And you can use any old dice shape you like, as long as they're all the same.

HeroQuest – the Contest/Augment system is a brilliant way to highlight anything and everything on the character sheet. It's all up for grabs.