Looks like you can get the REGULAR edition for $4.99. EDIT: Thanks u/BoxNz for pointing out that this is the regular edition.

https://smile.amazon.com/Fallout-New-Vegas-PC/dp/B00GXHIW2M/ref=sr_1_2?ie=UTF8&qid=1477226768&sr=8-2&keywords=fallout%2Bnew%2Bvegas%2Bpc&th=1

Fallout: New Vegas @ $2.49

If you haven't already, the original Bioshock and Bioshock 2 are $4.99 each

For some 'guilty pleasure' fun, you can get Saints Row: The Third