V.B.
I think it depends on how much you want to spend. My daughter will be 2 in a week and a half and we just got her the Fisher Price Rock, Roll n Ride tricycle. I did a lot of research online and read tons of reviews and this one seemed to be the best one for smaller kids. My daughter still can't quite reach the pedals (very close though), but she loves to scoot around on it using her feet to push her. It also has a handle on the back so that we can push her. A lot of the other ones we looked at were way too big for her and it would have been a really long time before she was able to reach the pedals. It was really cheap at WalMart (less than $35) and the seat is adjustable, so it can grow with them. The box says it is ages 2-5. Also, it's pretty low to the ground, so we haven't had any trouble with it tipping over yet.
The other really great trike that we saw was the Kettler. They are a lot more money (around the $90-100 range) and we decided we decided we didn't want to spend that much on a tricycle for her. However, my friend's twin boys had that brand and they were great for them. They just turned 5 and have big bikes now with training wheels, but they still ride their trikes sometimes, so it may be worth it since it lasts so long.
The biggest difference between the two is that the Kettler ones are metal with rubber tires and the Fisher Price one is plastic with plastic tires. I read that the plastic tires don't get the greatest traction, but it's very flat where we live, so we don't have any problems with that. If you live where there are any hills, you may want to go with the kind with the rubber wheels. Like I said...both got great reviews, so I would just say to search on Amazon.com or something for tricycles and read the reviews for each of them to see what the pros and cons are. Best of luck and Merry Christmas!