Yes, JustClick is yet another "ClickToCast" AddOn, but this one is slightly different. Based on the same concepts as EasyRaid (great User Interface and built as much as possible on top of WoW Foundations), JustClick revolutionizes the genre. Speaking about User Interface, I probably deserves an entry in the Guiness records book for that one. Actually, JustClick has no User Interface at all, neither slash commands! :-p How is it possible? WoW provides a great UI already, the one called "Key Bindings", why don't use it? This is exactly what JustClick does, the all UI is done with just one tiny modification of the WoW behavior allowing Left and Right mouse buttons in key bindings.
In case you don't know what is a "ClickToCast" AddOn, let me explain what JustClick does. Usually, you have to select a target before triggering any action (or select an action before clicking a target), this is the way WoW works. JustClick eradicates this targeting need, this is it, you are able to launch any action with Just One Click on any target. Believe me, when you are in a middle of a fight, one click (or key) saved to trigger an action is a lot. JustClick allows you to bind any action available in the Key Bindings windows to any mouse/key combos. For example, my priest uses a Ctrl-LeftClick to flash heal and a Shift-LeftClick to shield targets.
JustClick supports any target that you can see in the WoW standard UI (party members, raid members, pets, player, target and target of target frames) and every unit frames displayed by CT_RaidAssist, DiscordUnitFrames, PerfectRaid , XRaid, Sage, Perl Classic Unit Frames and of course EasyRaid. I'm sorry for the another AddOns I don't support yet, I plan to add more in the future though I think the best approach is to implement JustClick support into the AddOns themselves. The JustClick API is not going to change while the AddOns are often changing (ie: a new kind of frame is added). So, AddOn authors, have a look to the minimalist JustClick API (one simple function) documented in the JustClick.lua file.
However, any AddOns can benefit from JustClick without any modification. Since JustClick is based on the WoW Key Bindings, it can be used to trigger any kind of actions including macros and features added by another AddOns. Imagine you creating a killer-powerfull-intelligent-cast-healing AddOn, you add an entry to the Key Bindings windows to heal the current target, well done. Now you would like to be able to heal raid members just by clicking them. Don't reinvent the wheel, it's not that easy to implement a click-casting feature working with any kind of unit frame. Tell your users to install JustClick and you are done.
Finally, JustClick implements the so essential "SelfCast" feature, RightClick a spell from your action bar to cast it on yourself.