You'll see this a lot, at least on FullTilt... players, usually donks, betting e.g. 194 chips, or 777, or 299, or exactly one less than your stack. Some do it all the time, in which case I don't think it means anything, except that they're bored, or a moron. However, some players only do it sometimes, which you'd imagine means that it's how they bluff, or else how they bet their monsters.

Personally, I think that it's a bluff more often than not. The weird bet sizing is a clumsy ploy to try to intimidate and confuse the opponent, which is what bad players do when they're bluffing.

I just had a HU match with a donk who'd make standard bets and raises most of the time, but when making big raises or overbetting the pot would bet a number ending in 99. Although I say it's usually a bluff, I never really had anything to call him with, and he was doing it in situations where I could conceivably put him on a large hand.

Eventually, I decided to employ some level 3 thinking and give him a taste of his own medicine, but in reverse. Bad players always think that you play like them... so if he's bluffing when he bets that way, he'll think I'm bluffing if I play that way. Look at what he calls me down with - A high and a gutshot. Maybe he would have done it even if I'd bet normally, but I think he thought I was saying "I know you're bluffing when you do this, and I'm getting tired of it, so I'm going to run the same bluff on you to make myself feel better." Of course, that's exactly what I wanted him to think...

After that, I decided to annoy him to death by constantly raising to one chip less than his stack whenever I would have shoved preflop, just because his idiot play irritated me.

Full Tilt No-Limit Hold'em, 11+0.50 Tournament, 20/40 Blinds (2 handed) - Full-Tilt Converter Tool from FlopTurnRiver.com

Xopods (SB) (t952)
Fuckwit (Button) (t2048)

Xopods's M: 15.87

Preflop: Xopods is SB with K, K
Fuckwit calls t20, Xopods bets t199, Fuckwit calls t159

Flop: (t398) 10, 3, 5 (2 players)
Xopods bets t299, Fuckwit calls t299

Turn: (t996) 6 (2 players)
Xopods bets t454 (All-In), Fuckwit calls t454

River: (t1904) K (2 players, 1 all-in)

Total pot: t1904

Results:
Fuckwit had A, 2 (high card, Ace).
Xopods had K, K (three of a kind, Kings).
Outcome: Xopods won t1904

My SnG-playing friend had a theory that it's often a bluff since the stacks look bigger if a bet is made out of $100, 3x$25, 4x$5 and 4x$1 chips than just two $100s. This is obvs true for both live and online.