Hmm...I've had lots of great finds ($20-$50 titles for $5)....but if I have to narrow it down...

Box of 30 CV and 2600 games with several R4-R6's, most notable being Mr Do!s Castle - $6

Massive box of 54 SMS, SCD, genesis games (with the systems and power base converter) that included choice titles like 2 Alex Kidd's, and Golden Axe Warrior....$30

3 Looney Tunes 5 laser disc box sets ..... $4 total. I sold one of the sets for $98 on ebay a few weeks ago.. (ok technically not games, but I found them while hunting for games :P)