About a month ago, I made a trial account and created a baby Troll. I wasn't interested in exploring the limitations of a trial account, or testing out how trial accounts fare in PVP, or any of the fun things Cynwise has already talked about. (Seriously, if you want fascinating insight into the world of trial accounts, go read his posts.)
No, I made a trial account for a different, very simple reason.
I've been doing a lot of old raids lately for transmogrification purposes, and it's always such a bother wrangling up a guildie and getting them to switch to an alt so you can make a raid and go do Ahn'Qiraj or Tempest Keep or whatever. It's annoying and I dislike bothering them constantly for the assistance.
So instead, I simply leveled my trial Troll up to level 10 (the minimum level to join a raid group), and now whenever I want to go old-raid-diving, I simply open up a second WoW client, log in on my trial account, make a raid group and off I go! (You can be logged in on both your real account and your trial account at the same time.) Once the raid group has been created, I can safely close the trial client - as long as I don't drop group, it remains a raid group, even if the trial character has gone offline.
It's very easy to make a trial account - you just log into your normal WoW account on battle.net, and then you can add a new "starter" WoW account. It's tied to your normal email address and login information.
Then when you want to log into your trial account, you simply select the name of your trial account on the WoW login screen (from a dropdown menu) and that's it!
This is pretty handy for transmog fanatics such as myself. But why stop there? You can do so much more with your little trial characters!
Namely? As SPIES.
Story time: in my old MMO, Ragnarok Online, endgame was entirely PVP-based. It focused on guild vs guild PVP to control castles, which rewarded the controlling guild with special items and perks. There were only so many castles, which meant that competition was high, since the items were quite valuable, and in some cases, could only be obtained by owning territory.
Despite not having NEARLY enough players to properly take on other guilds, my guild took part in these battles through strategy and surveillance. Most guilds would sit and defend the castles they controlled, and maybe send out some attackers to assault others. It's very similar to Arathi Basin, really.
A conventional Ragnarok Online castle defense.
However, what we did was "defend" castles with only one or two people, whose only objectives were to harry and delay attackers long enough for the rest of our team to drop whatever they were doing and rush to their aid.
Something that helped us in this regard were dummy accounts with level 1 "spies." See, the castles were instanced, so anyone inside defending the castle's core couldn't tell when enemies entered, or if they were gathering outside, etc. But we just parked our little level 1 characters outside the entrance, unflagged, and kept those second clients open on another monitor or in the background. That way, we could see whenever an enemy team was entering the castle, how many they numbered, etc, and send an appropriate response force.
They also had an unanticipated bonus - intimidation! Quite often, a handful of attackers would run up, see the bizarre and mysterious level 1 toon parked outside, and stop, confused. They'd talk to them, ask them questions, emote at them, all sorts of things. At worst, they wasted valuable time trying to figure out what he was there for. At best, they got nervous and left without even entering!
So how can you spy in WoW? Well, quite easily. Trial characters won't help you in PVP, but they can provide you valuable intel on remote locations and on rival faction players.
I recently traded Keredria something like 7-8 Festival Lanterns for the Alliance equivalents (Lunar Lanterns) for the pet collectors in both our guilds. I was TERRIFIED of botching the neutral AH transfer, and of someone swooping in and nabbing them on the cheap. This was a lot of financial value we were flipping!
So to alleviate my fears, I grouped up with my trial character and summoned her to Gadgetzan. That way, I could watch Gadgetzan on her, Everlook on my actual character, and Keredria could watch Booty Bay to make sure there was nobody else at the Auctioneers when we swapped the lanterns.
My Troll is actually still there in Gadgetzan, so I can hop over and check the neutral AH whenever I want. She can't buy anything (no money, and I don't think they can actually buy stuff anyway), but she can view the items. If she spots something nice, I'll pop over on my actual account and buy it.
Speaking of spying, I also have a Human trial character, who I used during Love is in the Air to hang out in Stormwind and try to find players Fabulor needed for Fistful of Love. In addition to actually looking for them manually, I could /who Stormwind, Dalaran, Darkmoon Island, etc, and try to track down the specific race/class combinations I still needed. I actually completed the achievement by /who-ing Stormwind to learn the names of any Paladins in the city, individual /whos to find a Draenei one, walking around /targeting him to find out where he was, and then switching back to Fabulor to swoop down and rose petal him.
I've also created a few throwaway trial characters to pose for blog screenshots, when I wanted to capture a conversation. This way, I could take my time and take all the screenshots I wanted, repeating the conversation, without forcing some poor friend or guildie to sit there and endure my fussiness.
It can be quite convenient, having separate "cameras" available to take screenshots of your characters from different angles or positions!
In conclusion: raid slaves, cross-faction spies, and actors for screenshots. So handy - I love my trial account! And I bet there's more uses for them that I haven't even thought of yet. :D