Another vote for Saw here... it's not so much scary as it is interesting, but in that sense it's great. It fails on some SMALL aspects but overall it's much better than most recent horror movies.
Second hand lions was also all kinds of fun, especially if you love those oldschool pulp hero type things since that's what second hand lions pays homage to.
As for my own recomendations:
Im recomending Frida again since the movie still rocks after watching it again. It's got Alfred Molina (the villain from spiderman 2) as Diego Rivera, a super influential mexican painter who delved in cubism, communism and womanizing. His wife (Frida) is twice as much of a character, played by Salma Hayek she pumps out surrealist self portraits while seducing both genders and dealing with lifelong injuries from a trolley accident. Im not going to lie, it's an arthouse film, but probably the most entertaining one you'll see any time soon and it's got TONS of great talent in it.
B@d@$$$$$: Sorry about that but I HAVE to plug this movie. It's a dramatization of Melvin Van Peebles efforts to put out a revolutionary movie made by blacks for blacks back when that kind of thing was unheard of. You get to follow Mario playing his dad in a "warts and all" style and the pace of this thing is amazing, the movie just flies past you, especially if you have an interest in movie making.
Y tu mama tambien: One of the few Mexican movies made by my favorite Mexican director Alfonso Cuaron (He did the 3rd harry potter movie, the little princess and great expectations in america) and it's awesome. It's ***y, it's funny, it's introspective, it's political, it's very often politically incorrect and never preachy at all. I've known people who have been offended by the movie but never anyone who didint like it.