For a nice array of good-sounding electronic drum samples, try IR-909 (V. 1, roventskij; $4.99). It has a Roland-style step-sequencer through which you can trigger sampled kits from the TR-909, 808, 707, and 606 drum machines, among others. You can edit several sound parameters and store up to four patterns.
FEATURES, AT A GLANCE
Eight drum sounds
Individual pitch/attach/length controls
Six different sample packs (including original TR-909 pack, TR-808, TR-707 and TR-606, as well as Tech House and Karv)
Version 2 under development