I like cyanoacrylates (CA), epoxies, and more recently, urethane glue. It depends on the application. I love the speed of CA for general building of the airframe. Epoxy for high stress areas like firewalls, landing gear plates, etc. Urethane is great when you need a filling or expanding bond. It's great on foam, especially repairing when gaps need to be filled in. Great for sheeting foam wings with a vacuum bag. Also good for pin point hinges.

Here is some interesting info on cyanoacrylates.

[link=http://en.wikipedia.org/wiki/Cyanoacrylate]http://en.wikipedia.org/wiki/Cyanoacrylate[/link]