When I was a wee little thing (actually I was never wee, I was what you'd call...husky), the holidays brought visions of lots of things appearing under the tree on Christmas morning. Bikes, footballs, ponies and a replacement sister among other things. One thing that ranked very high on my list year in and year out was an aquarium. I can't imagine that too much has changed since then so for those of you facing the same request I thought I'd offer some advice and a few choice selections.
Let me put a few warnings in your heads right off the bat. First, don't let price tags scare you off, a good aquarium is one of the few examples of getting what you pay for. Second, pay no attention to the picture on the label. The label will show you what you CAN put in the aquarium, not what you SHOULD put in the aquarium. Third, a filter is important. Not only will it open you up to a variety of fish but it will cut down on your workload drastically AND it's just plain better for the health of the fish (note: a treasure chest with bubbles coming out of it is NOT a filter). And lastly, choose acrylic NOT regular plastic. One scratches, cracks and melts and one is...good.
I'll start with the Mini-Bow aquarium by All-Glass. It's acrylic, comes in three sizes (1, 2.5 and 5 gallons) and two colors (black and blue). The small size will restrict what fish you can put in there (white clouds, guppies and dwarf gouramis are among the most popular). Avoid goldfish. My goldfish rant will come at a later date, if you haven't subscribed to me yet, do so just to read that. They'll cost you between $25 and $55 but they're good solid systems and will fit on most desks or nightstands.
For those who have kids who can't get enough Disney, Tetra makes a 1.5 gallon aquarium that comes with a filter and a small light. It's very tiny and really only suitable for one Betta but the plastic statue of Nemo or Ariel in the center will make it sure winner with the 3 to 6 age range and at about $40 it won't hurt too much when you get to the register.
If you want your little kid to feel like a big kid go with the Eclipse. This is a product that I have had a love affair with for years and we're still hot and steamy to this day. Standard sizes are 3, 6, or 12 gallons. There is also corner model in a 5 gallon size. They only come in black but the three-stage filtration system is whisper quiet and the compact fluorescent lighting will really bring out the color of anything you put in there. It's acrylic (see how that works!) so you can throw a small heater on there and vastly expand the number of animals that can live in it happily. I've seen the twelve gallon model used to accommodate very small reef systems and I even used mine to keep an octopus! They can range in price from about $40 up to $130 depending on where you're shopping but they can easily last you as long as a standard glass aquarium.
I could go on and on...and on but I'm sure you, my loyal readers, have other things to do and I have to go make chili before the game tonight. Hope I've helped.