Rolemaster, 1st edition.
Easily my favourite.
While Rolemaster takes a lot of flak for its complexity of character development, these features evolved during the course of its second edition (and achieved breathtaking heights with RMSS).
But to its credit, Rolemaster used the same central unifying mechanic for everything in the game. It was easy to learn once someone explained it to you. Every player "got it" during the first session and did not have to be reminded afterwards. It was a model of elegance.
As a result, the spell system was extremely easy to learn, it was easy to use and it was extremely satisfying to play with.
Power Points
Rolemaster's spell point system was inventive and still stands the test of time.
Power Points: A character had a base number of power points, determined by his or her primary stat x their level.
This number was their base power points.
A common magic item called a power point multiplier increased the available number of power points. The higher the power point multiplier, the more kick-ass the nature of the item. A common power point multiplier was a x2. Artifact level power was x5 or x6. The One Ring was a x10.
So an adept Magician with a high empathy had a value of "3" power points per level. At 5th level, this gave him 15 power points as a base. If he had a x2 power point multiplier, this would increase the number of power points to 30 per day.
Another common magic item feature was the Spell Adder. The adder gave the caster a certain number of "free" spells per day. Those spells could be cast without reducing the available number of power points.
You could never, ever, have more than one power point multiplier or spell adder to which you were attuned at any one time. Obviously, if the same "plus" could be used to cast a 10th level spell or a 1st level spell -- you tended to use your spells adder "plusses" for high level spells and spent your points on the lower level ones.
So if the item acted as +3 adder, x2 power point multiplier? You now know what that ubiquitous item does, don't you? A model of elegance and unified game mechanics.
So that's power points.
Spell Casting
How many power points did a spell cost to cast? Simple. A spells costs a number of power points to cast equal to its spell level. Always.
That's it. But you heard Rolemaster was complicated? It could be, but the base mechanics were always extremely elegant and easy to learn.
A 7th level spell costs 7 points. A 3rd level spells cost 3.
So that's the power point cost system. A one sentence rule. A model of elegance.
Preparing Spells
The rule is simple. There is no spell preparation. For anybody. It's all spontaneous casting, all the time.
You could cast a spell you knew, if you had the power points available (or a spell adder "+" available ) to do it.
Time it Took to Cast a Spell
A spells either took 3 rounds, 2 rounds, 1 round to cast -- or in some cases, specific spells could go off instantly.
If you were six or more levels higher than the spell you were trying to cast, you do it one round. If you were three to five levels higher than the spell you were trying to cast, you could do it in two rounds. Otherwise, it took three rounds to cast. (Technically, two to "prepare" and one to "cast").
If you rushed the spell, this added greatly to the risk of spell failure. You could seriously strain yourself and even, on an ridiculously unlucky roll, knock yourself into a coma if you rushed and failed your roll when casting a spell.
If you over prepared, you could use the extra-preparation time to offset the penalties that came with casting a spell level higher than your own. For utility spells and spells outside of combat, this made those magic resources available to players outside of combat. Very, very handy.
Great fun.
Realms of Magic
The types of magic were separated into three distinct realms. Channeling (Divine) Essence (Arcane) and Mentalism (Psionics, sort of).
Some spells combined the realms. Sorcery, a particularly nasty form of destructive black magic, blended Channeling the power of an evil god with Essence, for example.
But for the most part, the spells fit neatly into those three realms. Mentalism didn't use a different system than Channeling or Essence. While its effects tended not to be as flashy and also tended to effect only the caster, the underlying spells system for it worked exactly the same, using exactly the same learning, casting and resolution mechanic.
for the most part, Mentalism spells felt like spells and not like Psionics. So much so that in SpaceMaster, ICE's sci-fi setting, they invented Psionics lists with some very different powers and different named psions for flavour purposes.
There wasn't any reason for a FRPG spells system to have spells which powered energy weapons or supplemented starship navigation, for example. So "Psionics" in SpaceMaster had those features while Mentalism didn't.
But the underlying system in terms of mechanics and crunch was identical. It worked very well.
Learning Spells
This got a little tricky, but it was still relatively easy in Rolemaster to do. (In 2nd edition -- it got a lot more math heavy)
You learned spells from "lists" based upon your class. Your class was deemed to be either a Pure, Hybrid, Semi-spell user or Non-spell user.
Spell Lists in each of the Realm of magic was divided into one of three categories, an Open list, a Closed List, and a Base list.
As you might expect, the most useful spells were usually on the "base" lists, followed by powerful spells on the closed lists. The Open lists tended to be spells which were not as powerful, when looked at as a whole.
Your eligibility to learn spells from a given realm was based upon your class. Pure Spell users had access to easily learn spells from their own realm. Hybrid spell users casting from two realms of magic had a hard time learning closed lists from either realm, and semi- spell users learned spells more slowly. Non-spell users spent a lot of development points to learn just a few spells -- but they could do it if they wanted to.
It was sort of Wizards vs. Bards in 3.xx. A Wizard in 3,xx would be a Pure spell user, whereas the Bard would be more like a Semi-spell user.
Overcasting
In 1sr edition RM, you learned spells usually 10 levels at a time. As such, you routinely knew spells which were above your own level. If you tried to cast a spell beyond your level, this could be bad. As in "crossing the streams" bad, to paraphrase Egon.
Because casters in Rolemaster frequently knew spells which were above their level to safely cast, this provided a resource that PCs could dare to use in extremis. In turn, this provided the PCs with resources to meet challenges which were well beyond their own "normal" power range. A bad roll of the die and you could easily knock yourself out during a fight by trying to cast a spell that was beyond your power.
Nevertheless, saving certain "meta-game" re-rolls during a session to attempt a spell overcast against a BBEG was one of my favourite aspects of the system. It allowed PCs unpredictable access to considerable heroic power once a session for a boss battle, but otherwise kept a lid on the PCs overall power when dealing with everyday encounters. This was exceptionally AWESOME. One of the best things about Rolemaster in fact. I miss it - a lot.
Why? It produced tension and HEROIC play sessions as a consequence of this feature of the rules. It rocked.
You could fumble or critical with a spell. You knew some spells which were beyond your ordinary abilities to reliably cast.
Spell Exhaustion
In Rolemaster, whenever you had your hit points drop -- or your power points drop -- past certain threshold levels nased pon your maximum normal points (75%/50%/25% of maximum) you suffered a cumulative -10 to your roll for every threshold. This simulated your being hurt/exhausted -- or both.
So the system even simulated casters becoming fatigued by casting their spells. This was also very cool simulationism -- but it came at the cost of fiddly record keeping. This was one of those aspects of RM that would have greatly benefitted from automated computerized tracking.
Great idea but VERY fiddly to use in practice.
Criticals
Finally, certain spells could be learned and specialized in just like weapons. A magician would learn to specialize n a "directed spell", equivalent to a ray attack in 3.xx -- and increase his chance to hit and do damage with that particular attack. Several of the iconic spells had their own chart of course. The biggest, baddest, directed spell-of-them all was not the fireball -- it was the Lightning Bolt.
There was a lesser electrical ray attack in Rolemaster called the shock bolt. But the out-and-out ass-kicking happened from the Lightning Bolt.
A Lightning Bolt in Rolemaster was a kick ass spell that you had to be at least 10th level to safely use. It blasted things to smithereens. A 150+ result when casting a Lightning Bolt was death and woe to the target. 35 points and an E class electrical has a good chance of killing ANY human sized opponent in the game, regardless of their level and hit points in one shot.
100 on the E class critical chart? "All that are left are bits of charred teeth and bone. +50 to your next attack"
BOOM!!
Spell Parry
If you learned how to do it, you could parry spells attacks to deflect them. This was exceptionally cool, although the action economy in Rolemaster almost always favoured a full attack instead of defence. Still, for some boss battles, this was always a central part of the attack plan.
You could parry spells, jump to avoid them or gird yourself in resistant armour protected by spells of protection.
All of that was aimed at avoiding a 150+ result on the directed spell attack chart coming your way.
But if your opponent rolled extremely well? Death lurked at every doorway.
I loved Rolemaster.