Other than storage, I think that is going to depend on your priorities.  I don't plan to use mine for more than a night or two at a time and usually where there is a shower.  So, I gave up the bathroom and it's been fine.  NO tanks to worry about this way either.  We put in a sprayer on the sink for washing hair and that works really well.

I really wanted lots of drawers and we took out the stovetop and got more counter space and added a big drawer there.  I needed a place for hanging clothes and the one we got didn't have a full length closet so we added curtain rods to the cabinets in the nose (which is a really nice option).  We have a mid size fridge with separate freezer, which my friends all say I will totally appreciated someday, but I haven't yet.  We wanted a removeable table and got a 1/2 table, with a couch, because I wanted a place to read, write, and eat.  Although we haven't removed the table for the extra floor space yet!  The walkthrough to the horse area is a must I think, as you can then use the horse area for a mudroom.  Got the awning, but haven't used it yet. 

I was more into what was in the horse area.  I really like the manger storage.  In Texas, drops front and back, or plexi in the back are important.  Stall space was important since my horses are fairly substantial.

Hope that is helpful.  Storage, storage, storage.

  I put in an order for a stable boy, a beer fridge and an automatic clean up system but I am still holding my breath. 

  I am in the process of rebuilding my lq and so far have to agree with the storage part.....big time.

Back to the horse area - I'd have loved to have the rumber flooring and we added fans and insulation to the horse area.  We also have a cowboy shower which we added a pan with hose out the back of the trailer, and a removable shower curtain for (I asked for help from this forum and got it!). 

If you are going to take other people, I saw some really neat bunk beds that doubled as storage (there's that word again) when not being used as bunks.  Outside faucets and lots of lights are nice.  I like the windows since that makes being inside not so stuffy.

Big frig with freezer.  Generator with remote start.  combo micro/convection oven.  Walk-thru door, escape door on first stall, stud partition on first stall.  Mangers, on 8' wide.  Pocket door to bathroom. Awning.  Naturally AC and furnace.  Use this stuff all the time (heat or ac depending on season) every time.  Awning has deflapper and full length serious tiedown.

Can you tell we primitive camp?  Have been gone 3 weeks without a hookup.

It really depends on what you do with your rig.

My trailer has never seen a fairgrounds. Never been to a horse show. I use mine for camp trips to the mountains.

radio or TV have no reception where I go. So unless I have a DVD or CD player they are worthless. I do use the CD player in mine (the kids more than I) Don't have or miss a TV. I go to the mountains to get away, not watch TV

I do use the awning. Beside the shade it keeps the area in front of the door dry from occassional thunder storms

Rarely do I use the shower.  I just can't carry enough water to allow me or family members to use it. If I camped in campgrounds with hooks ups that would be different, maybe I would. But in primative sites, there is not enough water to take a shower.

I use the microwave a lot. I rarely use the stove top. We do cook a lot out side under the awning. BBQ or Dutch ovens.

I have a 6.0 Fridge/freezer combo.  Use the fridge ALL the time.  In fact I keep water/pop in it all summer. Even if I'm just working in the yard, I sometimes grab a bottle of water out of it. If my wife and kids come camping, they use the freezer.  Ice cream/popsicles or just ice cubes.

Coach that folds out into a bed.  Gives us a second bed for my daughters to sleep on.  Or when I go hunting, I can let my hunting buddy sleep on it.

Furnace - absolutely. I have many many more cold nights than ever a hot night.  I've used my A/C one time. I use my furnace almost every trip. It's much cooler at 8000 foot elevation. It's nice to turn on the furnace and warm up the trailer before you get up.  It would not bother me at all to not have an A/C unit.

I love the storage under my managers.  I hate that my horses can not turn around inside the trailer because the managers make it too narrow. ( my trailer is 7'3" wide) But I would not give up the storage.

Pass through door to horses.  Like the post above, I use the horse area as a mud room.

Drop down windows head and butt. Can't get enough ventilation in the summer and when it's 10* in the winter I'm sure the horses appreciate that I can shut the windows.

I keep my portable generator in the truck bed.  It would be nice to have a built in Generator. But I won't pay the price. I use my generator for 30-45 mintues at dinner time (mostly to run Microwave or a george forman grill).  It also recharges my battery .  I may turn it on in the morning long enough to microwave some oatmeal or nuke a pastery or cinnimon roll.

A Horse water tank. I carry 30 gallons of People water and have a seperate 35 gallon tank in rear tack for the horses.

One key for all Locks and doors.

Jiffy jack for tire changes. Spare tire, dual batteries, dual propane tanks, I have an electric jack,did't think it would be a big deal, but the trailer came with it. Love it.

HiTies.  I tie my horses to the trailer a LOT at night. I am a light enough sleeper than I don't sleep at all if I tie them to the rings. With the HiTies the horses can move around and I don't feel the tugging on the trailer all night.

I don't like roof top racks.  Too hard to get the hay up and down. I also drive too many forest service roads with low hanging tree limbs that tear that stuff off.  I load the manager up with hay and put 3-4 bales in the truck bed,  It's all I usually need. If I need a little extra, Several bags of pellets easily fit under managers. But I am rarely gone for more than long weekends. Just take enough feed for 3-4 days. Plus most of the mountains that I go to have grass that I can hobble my horses and turn them loose.

My favorite must haves

Awning

Outside Speakers for radio

Steel floor with rhino lining

bars on drop down windows that stay up when you drop the window on the horses

AC

No heat strip! Everyone complains that they dont work

Walk through door to horse area. You will be suprized how much it opens the place up.

fold down bunk.

storage

on board quite generator

hay rack

seperate bath room with pocket door

I am sure there are more but I can not think of them right now. Hope this helps!

Hydraulic hitch is fantastic!  I can hitch up or unhitch in a couple minutes. No cranking (electric is cheaper, but slower, but a huge improvement over the cranking)

I trail ride/camp and about 3/4 of the places are primitive, so I need propane to run stuff.  My generator is in the truck bed so I don't use it all that often as it gets heavy to lift out & set up.

agree with everybody else on most of the stuff:  pass through door, pocket screen door, sink, hot water heater, AC (important in Fla), use a $20 electric heater for the few cold nights, cowboy shower, dinnette, storage( never have enough) fridge, awning, & I have two rotating small fans that I love.  One covers the dinette sink cooktop area, the other in the GN. 

I board so I have to bring my food to the trailer in a cooler.  I put the food in the fridge and leave the drinks in the cooler as they stay colder & have to go in this more often.  I freeze 1/2 jugs with water & this lasts much longer than ice cubes, though I do bring ice cubes for drinks.  Bag up the ice cubes & keep in the freezer.

make sure you get propane so you are self sufficient.  Propane will run the fridge, hot water heater, cooktop, and furnace if you need one

wish I had: storage mangers, push start installed generator, shower in the LQ, and windows that crank out.  The sliding ones have to be closed when raining or it comes inside.  My next trailer will have these options if I can ever afford to buy it and pull it with these escalating diesel prices....

Toilet and shower are first due to being a lady and camping alot.  Next my hydraulic jack will not own another lq trailer without it.  Then, sink, awning, microwave, refrigerator and water tank.  I also have a built in cd/am-fm stereo which I use alot. And like several others would love to have a walk through between lq and horses but I just traded down for a simpler lq and it does not have one.  My other one was loaded and also financed for 12 years.   

HOLDING TANKS:

Get the most fresh water you can and the largest holding tanks you can.  I have a 34 gallon fresh water  tank in the  trailer and a 55 gallon tank for my truck and only 12 gallon gray and black tanks.   

Dark curtains are good if you want to sleep beyond sun up, we are missing those too.