One-step sparring is a mainstay of karate training. In traditional wado ryu they are usually done using three steps, but a few years ago we stopped doing the sanbom kumite and instead just used one attack.
The wado ryu ippon kumite sets were develped by Sensei Suzuki and include 1x soto uke, 1x uchi uke, 4x jodan uke and 6x maegeri.
Our club doesn't stick too closely to traditional wado canon. We use the katas, basics (junzuki, junzuki no tsukkomi, nagashizuke etc etc) and we have the 10 kihon kumite.
The rest of our training is pretty freestyle with lots of pad work, pairs work, kata study, attack-defence work, throwing, joint locks and kakie. But recently we spent some time on ippon kumite, namely the four jodan defences which are the most interesting of the lot.
We used them as a preview for kihon kumite.
The attacker begins in a fighting stance andhoes straight into the attack with a jab. The defender is either in a fighting stance or a natural stance and simply blends in with the attacker. We make use of sanchin stance and we like to play with variations and additional techniques.
A few years ago Vince Morris wrote an article about ippon kumite. He varied it slightly to make use of close-in techniques, realistic attacks, mawashi uke and so on. We incorporate the same movements into our ippon kumite.
Sometimes a few little changes to "old hat" training methods can produce some good training and development. I'll see if I can get some photos done and post some more specific information about our methods.