[quote name='Dr. Strangepork']If all you have left is $18, I would save it for food or some other necessity.[/QUOTE]Video Games > Food.
Bejeweled 2 (Fun and addictive if you are into it)
Bionic Commando Rearmed (Very tough, but lots of fun to play)
Blast Factor (the game is pretty fun once you purchase all the add-on content, but may not appeal to everyone)
Calling All Cars (Fun to play with others if you have local friends and many controllers)
Crash Commando (fun multi-player game)
Cuboid (Might not be worth the price, but many say it's fun)
Echochrome (very interesting puzzle type game)
Everyday Shooter (fun game and very interesting)
Fatal Inertia EX (the game is a bit expensive and not as good as Wipeout HD, but still good)
Geon (cool concept, but not for everyone)
Go! Sudoku (If you are into it, good purchase)
GTI Club + (Sucks that it has just one track, but a great Arcade port)
High Velocity Bowling (fun bowling game with online play)
Lumines Supernova (great puzzle to play)
Magic Ball (Pretty good game like Breakout)
Mega Man 9 (If you can’t get into NES games, avoid, but if you can appreciate 8 Bit graphics and tough difficulty, definitely buy)
Mortal Kombat II (while it may not be the best classic port, still fun to play)
PixelJunk Eden (might not be for everyone, but cool style)
PixelJunk Monsters (very fun RTS type game, similar to Tower Defense or whatever it's called)
Prince of Persia Classic
Puzzle Quest: Challenge of Warlords
Ratchet & Clank Future: Quest For Booty (If you beat ToD, this game is great to play, although short)
Siren: Blood Curse (awesome survival horror that's fun and scary)
Soldner-X: Himmelssturmer (Good shooter, but hard)
Super Puzzle Fighter II HD (Very awesome puzzle game that’s fun)
Super Street Fighter II Turbo HD (Very awesome 2D fighter)
Super Stardust HD (Very downloadable game that's addicting)
Tekken 5: Dark Resurrection Online (Best version of Tekken 5)
The Last Guy (Pretty cool and interesting downloadable game)
Wipeout HD (Very awesome racer)
Bold means definite
PS1 Games
Suikoden
Wild Arms