Any decent buggy!

Durango,Kyosho,Losi, AE etc....

Weather permitting its still outdoors this week.

For indoor race we use the same as outdoors! We've got a good sized indoor track - basically a whole school sports hall, so we can run 1/10th buggys and shortcourse even with quite powerful motors just fine.
Be aware that the surface will be a mix of grippy carpet and slippery polished floor. The difficult part will be making the car work well on both. 4wds are a little easier to manage on the slippery stuff, but also tend to grip roll more on the carpet.