If I had debt costing me more than perhaps 3.5% or so, I'd probably pay it off.
If I lived in a region with attractively priced rental properties, I would consider buying one using the $10k plus other funds for a downpayment.
Otherwise, I'd hold onto the $10,000 for investing and wait for better opportunities to buy into the market.
I don't believe in market timing for my ongoing contributions (401k, IRA, etc) but for lump-sump investments I would prefer not to buy into the market when many different metrics suggest that if the market isn't overpriced, it is - at the very least - not sufficiently cheap to be buying broad-based indices or funds. There are occasional opportunities out there in individual stocks, but the average stock (which is all an index is) these days is priced on the pricier side of "fair", I think. 5 years of steady gains, dynamite short-term performance, and a lack of attractive alternatives have made stocks the place to be.
Before anyone asks, I'd keep the money in a money market. Yes, I'm aware that the money market would earn nothing (to be precise, it would earn about 0.01%), but I'm OK with that. The point of holding cash (for me at least) is not to earn a wonderful rate of return. It's because you want the money to be there when you reach for it. At some point in the next few years, it's likely that stocks, houses, bonds, or some other desirable asset class will be sufficiently cheap to buy in. At that point, I would prefer to have all $10,000 available.