It’s easy to do on eBay. Whatever you’re looking for, whatever you want to buy, millions of items on eBay are returnable. Before you bid or buy an item, check the seller’s return policy, then follow these easy steps to make a return. To stop a particular member from being able to bid on or buy your items: Go to the Block bidders or buyers from your listings - opens in new window or tab page. Enter their username. (You can add up to 5,000 usernames.). Select Submit.
For the record, eBay changed their system to make sniping essentially pointless several years ago. Instead of just making a bid, you submit/commit the most that you are willing to pay, then it accepts the lowest amount for you to win. If someone makes a bid, it automatically raises your bid to match up to your maximum.
Therefore, sniping doesn’t work if someone else has a higher maximum bid than you, and in fact, it would blow the auction for you to wait until the last second because you won’t have enough time to see their auto-bid outbid your snipe and react. (Yet lots of people still do it.) – Jul 24 '14 at 21:06.
Reading your tags it seems like you are looking into something with iOS and Android support. I use for my own sniping purposes. It's available for iOS (offers both iPad and iPhone support) and Android as well. I like it because it allows me to browse eBay and import my Watch List, and also supports groups (where you set a number of snipes, then the sniping stops after you win a certain amount of items). The reviews look good for both iOS and Android. There are some users who are not happy, but developers looks active on that by properly suggesting good ways on resolving it. Whenever you have an issue or just a simple question their support is fast when you try to contact them.
Update regarding reliability: I used Myibidder for quite some time. Not sure when I started but I pushed several hundreds of snipes for sure.
During this time I got a few failures only. One failure was because eBay reset my password for some weird reasons. Another failure was because of network time-out (I think eBay was having some performance issues a few years ago. Never saw it again).
One more failure was when eBay made some huge changes on their website, Myibidder reacted quickly but I was lucky enough to have my snipe right in between. Update regarding the pricing: I see they have two Android versions right now: free and paid.
The paid version has some additional perks which I don't use. They also have two iOS versions: PPS and non-PPS. Their description said PPS is Pay Per Snipe. It seems like the non-PPS version offers unlimited sniping.
I personally use PPS version because it comes cheaper overall. They charge for won snipes only, and their fees are the lowest I could find. You could always replenish snipes using in-app purchase. I see no problems paying for a great service, I save money on sniping after all.
And here is the bonus: Myibidder has the which is free. They said this version will always be free.
I used to use Web version on my iPad before I switched to the native app.