"Spell Range" info in the tooltips and "spell tooltips of enemy champions" accessible in game.
So... I had the matchup Annie Vs Lux recently. I was the Annie. I can't remember the last time I've ever played against a Lux as Annie so I've compared Annie's and Lux auto and skill range on the wikia. It looked good for me since my Disintegrate(Q) and Incinerate(W) range have the same range as my attack range, which is a huge: 625. So if I ever get "Light Binded" followed by an auto attack from Lux I should at least be able to to put out some damage back to her. But as I tried to cast my Q on Lux while being snared and auto'd, nothing happened. I tried several times to auto + Q Lux but the Q never happened.
After the game I was curious about what was wrong and created a custom game with a friend to test the skills and range with those 2 champions. And the blue range indicator of Annie's Disintegrate(Q) was indeed lower than her attack range. I let Lux Light Bind me again and go in her attack range, I wasn't able to cast Q again, but I was able to just about reach her with my max range W, which seem to have about Lux attack range: 550. When I compared the range indicators of Q and W, the max range of W seem to have about 25-50 more range than Q. So If Lux auto range: 550 is right, Annie's max W range should be about the same and her Q is less than 550.
Both leagueoflegends.com and leagueoflegends.wikia.com say that the spell range of Annie's Q and W are 625. They are wrong. So what is the official number? I would love to see the spell range as a number shown in the tooltips in game. You can check your champions auto attack range by pressing Strg+C I think or clicking on the portrait. As you auto alot while last hitting, you get used to your attack range pretty fast, and if you know how far your spells can hit compared to your auto range, you are be able to tell if you can take trades or not.
TL;DR: Pretty much the title. (Wikia range numbers seem to be not quite right, at least in Annie's case). I would also like to see a short champion skill tooltip for enemies you are facing in the current match, which you may not know yet, because you are new to the game. It should show at least how much the base cooldowns and the range of their skills are. I think the best place to add this feature is while the Tab window is open when you mouse-over the champion you want to check out. This feature can improve your laning phase a lot especially in top and mid lane, if you are not sure about your matchup. It will be easier to get to know new champions, even if you didn't play them yet or learn something new about a champion you thought you already knew everything about
Example: I play Annie Vs Talon. I'm not sure if I can harass Talon without getting a full engage from him. So I tab fast mouse-over his portrait and check his skill range on Cutthroat: 700 (If the wikia range is right). Since all of my Abilities are lower than his engage, this matchup could be dangerous for me if he reached at least level 3. It also tells me that I have a lot of time to harass him after he engaged on me with the long cooldown of his E. And his main harass spell W has a range of 600 which is slightly lower than my attack range.
Thanks for reading, I hope some people share the same opinion about this.