This is my submission for Cold's Gold Blogging carnival this month, the subject of which is Ideal Alts. Now Cold did a fairly comprehensive series of posts on this subject & my first choice was in there so it's taken me a while but I think I've found one he didn't cover! The rep grinding rogue :-D
To be fair, this probably isn't the most effective alt for gold making but rather in speeding up & reducing the costs of reputation grinds (thereby saving money & you get back to the AH quicker!) lol.
Ok, so my thoughts processes are like this - human for the racial which gives +10% reputation gains & rogue for their ability to stealth & pick pocket. I know druids can stealth & I did consider them but it's the pick pocket ability that swung my decision (more on this later).
As for professions - well, seeing as most of the Burning Crusade factions have dungeon grinding as a way of gaining reputation, I think Enchanting is a must have especially if your rogue is high level & going to solo these dungeons regularly - disenchant everything & either sell the mats or use them for scrolls if more profitable.
For a second profession, there are definite arguments for going with skinning as leather & hide is always a good seller at almost all the various levels however, my second choice would be Tailoring. Why tailoring - because there is always a lot of cloth dropping in dungeons & you can use it to craft items for skill ups then disenchant those same items for enchanting mats.
The second bonus for tailoring is the Northern Cloth Scavenging ability which means that when you grind through the Northrend dungeons, you'll be picking up a shedload of frostweave. At the current time, frostweave cloth sells for about the same if not slightly more than Embersilk Cloth so good money to be made there too.
So why does the pick pocket ability of the rogue make this the perfect choice? Well one of the reputations for the Insane in the Membrane achievement is the Ravenholdt one - the only way to advance this rep to exalted is by handing in Heavy Junkboxes. Why pay a rogue to do this for you when you can do it yourself on your very own stealthy killing machine?
The beauty of the stealth ability is that if you don't have time to kill everything in the dungeon, you can stealth past all except the ones you want, in most cases, the bosses but sometimes it's not the boss that gives you the rep items. You can also stealth past everything to collect the Sanguine Hibiscus in The Underbog for Sporregar rep.
From a gold making point of view, you should pick pocket everything then kill it - the gold in the junk/lockboxes isn't huge but it all adds up by the time you finish all these reps. You can also get some nice items - at 85, every rogues' dream weapons drop only from pickpocketed chests (krol decapitator & spinerender) albeit at very low drop rate.
If you really want to make the most gold out of this alt & haven't yet levelled one - consider stopping your XP at 80 - you can get the faction tabards & use the dungeon finder to run Northrend dungeons (in cata greens of course!) for the rep & for all those lovely Wrath enchanting mats & cloth. For the truly serious achievement chaser, there are also various mounts available in these dungeons & for purchase from Quartermasters once you are exalted. Don't forget the Argent Tournament either - money, pets & mounts from the dailies as well as rep & titles.
Unfortunately my own rep chaser isn't my rogue, tailor or enchanter & my rogue isn't human, tailor or enchanter so I kinda messed up there! lol