Depends on the interest rate.
If you're talking about a really favorable loan, where the interest rate is less than I could safely expect to withdraw if I invested the money wisely (4% should be safe in the long term, 5% will eventually dig into the principal), I'd invest the lot, pay off the interest with my investment returns, and skim off the margin.
There probably wouldn't be much of a margin, but if I could skim off just half a percent on average, that's still a cool $5000 extra in Christmas presents every year.
In the more likely case that the loan came with a higher interest than that, I'd immediately pay it back in full, unfriend whoever got me drunk enough to sign it in the first place, and keep doing what I was doing.
(I know this is a tedious answer, but insisting that it's a loan rather than a gift makes the question pretty tedious.)