Alinco and Alinco Buffs FTW ... they do everything LTxi does and more, the only difference is you can't macro at all with Alinco (U or A). It tracks mobs, portals, trophy items, chests, etc. It'll even auto-loot and auto-salvage for you. It also has a feature where you can search all char's on the account for certain item. E.g., someone in your clan asks for a major war magic ring. Just type it in and it will tell you which chars have that item in their inventory (Reminder: you have to set this feature up by logging each char in and running the scan feature first).
Another great plug-in is Target Info - whenever you click on a creature, another player, or yourself, it will tell you what debuffs have been cast on them. You have to be within a certain distance of the spell when it was cast, but it will track ALL critters in the area. This is amazing for Colosseum use.
Third, Skunk Vision is amazing. It does several things, what I use it for is to highlight impassable water and mountainsides. Never get stuck again!!
Fourth, MiniMap is prolly the single most undervalued plugin in the game! It actually draws the dungeon map on your radar as you move through it. When you pass by a wall, it turns from white to blue so you can tell EXACTLY where you have been and where you have not been in a dungeon.
Past those, I also use Mule Trade It! for my tradebot and also Lifetank when I want to A(get that ... ATTENDED)cm

LTxi is not designed for UCM which is against the Turbine CoC

(EDIT -> Oh yeah, QuestTimer is awesome. Never be in doubt when your timer is up for your favorite quests

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Hope that helps!