Just sat down to 48 minutes of Portal, it was pretty easy for the first few stages, though the real difficulty was doing multiportal trajectory jumps, made me feel sick, plus theres there bit with the 2 diagonal pieces of wall and bouncing balls. :O
Hmm, just throwing it out here, but the 2 (English that is) Boktai games are pretty obscure, their main gimmick is that it has a sun sensor on the cartriges, but the first game in the series had a heavier influence in stealth, its produced by Hideo Kojima. i personally thought the puzzles were more complicated in the first game than the second, though it does have multiple ways to get to the end whereas the second game is pretty linear, the main quips with the both of them is that they both absolutely require the Sun at specific parts. (such as the beginning of the first game, or at a plot relevant bit in the 2nd)
Another game i menctioned in the first post was Gitarooman Lives, an unusual rhythm game that was developed by IniS (think Elite Beat Agents), you hold the control stick in a certain direction to make sure it 'traces' the note lines, it has a few phases where it switches to rhymnic button pressings and trace phases, the music is catchy and can get difficult really quickly. (does sort of give me a PaRappa vibe slightly, with little emphasis about rapping and more about survival)
A video of Gitarooman's gameplay if you're interested.
Hmm now that i think about it, placing youtube videos inside spoiler tags makes it look neater, plus i dont think it uses time to load the applet up unless you flip open the tag.