My favourite game has to be poing, which is a freeware arkanoid clone but it is so much more.
It has loads of innovative ideas and cuts out the pointless powerups which litter other clones. Cool computer generated music, funky graphics (for an arkanoid game) and sooo playable. Anyone who hasn't tried it go to Aminet now!! Oh and poing5 is better than poing6 in my opinion so get poing5. (poing4 was good but i can't find it on aminet.)
n.b. you will need a good mouse and good reactions!