On the more expensive side you can look at MakeNoise Morphagene (want one) or Mimeophon (Got one) lets you hold a loop in its buffer and if you are clocking Mimeophon you can make it play in time with other parts and get as creative as you like.
I do fancy a 2hp Loop though, maybe 2 of them for Stereo would be fun.
Enjoy your spare HP, don't rush to fill every last space, this is not like filling sticker books. Resist the urge to 'complete' your rack, its never complete so just relax.